diff --git a/python/taichi/lang/matrix.py b/python/taichi/lang/matrix.py
index 2904c8cda0ae6..a99c218008418 100644
--- a/python/taichi/lang/matrix.py
+++ b/python/taichi/lang/matrix.py
@@ -1,3 +1,4 @@
+import functools
 import numbers
 import warnings
 from collections.abc import Iterable
@@ -102,25 +103,44 @@ def prop_setter(instance, value):
     return cls
 
 
+def _infer_entry_dt(entry):
+    if isinstance(entry, (int, np.integer)):
+        return impl.get_runtime().default_ip
+    if isinstance(entry, float):
+        return impl.get_runtime().default_fp
+    if isinstance(entry, expr.Expr):
+        dt = entry.ptr.get_ret_type()
+        if dt == ti_python_core.DataType_unknown:
+            raise TaichiTypeError(
+                'Element type of the matrix cannot be inferred. Please set dt instead for now.'
+            )
+        return dt
+    raise TaichiTypeError('Element type of the matrix is invalid.')
+
+
+def _infer_array_dt(arr):
+    assert len(arr) > 0
+    return functools.reduce(ti_python_core.promoted_type,
+                            map(_infer_entry_dt, arr))
+
+
 def make_matrix(arr, dt=None):
     if len(arr) == 0:
         # the only usage of an empty vector is to serve as field indices
-        is_matrix = False
+        shape = [0]
         dt = primitive_types.i32
     else:
-        is_matrix = isinstance(arr[0], Iterable)
+        if isinstance(arr[0], Iterable):  # matrix
+            shape = [len(arr), len(arr[0])]
+            arr = [elt for row in arr for elt in row]
+        else:  # vector
+            shape = [len(arr)]
         if dt is None:
-            dt = _make_entries_initializer(is_matrix).infer_dt(arr)
+            dt = _infer_array_dt(arr)
         else:
             dt = cook_dtype(dt)
-    if not is_matrix:
-        return impl.Expr(
-            impl.make_matrix_expr([len(arr)], dt,
-                                  [expr.Expr(elt).ptr for elt in arr]))
-    return impl.Expr(
-        impl.make_matrix_expr(
-            [len(arr), len(arr[0])], dt,
-            [expr.Expr(elt).ptr for row in arr for elt in row]))
+    return expr.Expr(
+        impl.make_matrix_expr(shape, dt, [expr.Expr(elt).ptr for elt in arr]))
 
 
 def is_vector(x):
@@ -241,48 +261,6 @@ def _set_entries(self, value):
                 self[i, j] = value[i][j]
 
 
-class _MatrixEntriesInitializer:
-    def pyscope(self, arr):
-        raise NotImplementedError('Override')
-
-    def _get_entry_to_infer(self, arr):
-        raise NotImplementedError('Override')
-
-    def infer_dt(self, arr):
-        entry = self._get_entry_to_infer(arr)
-        if isinstance(entry, (int, np.integer)):
-            return impl.get_runtime().default_ip
-        if isinstance(entry, float):
-            return impl.get_runtime().default_fp
-        if isinstance(entry, expr.Expr):
-            dt = entry.ptr.get_ret_type()
-            if dt == ti_python_core.DataType_unknown:
-                raise TypeError(
-                    'Element type of the matrix cannot be inferred. Please set dt instead for now.'
-                )
-            return dt
-        raise Exception(
-            'dt required when using dynamic_index for local tensor')
-
-
-def _make_entries_initializer(is_matrix: bool) -> _MatrixEntriesInitializer:
-    class _VecImpl(_MatrixEntriesInitializer):
-        def pyscope(self, arr):
-            return [[x] for x in arr]
-
-        def _get_entry_to_infer(self, arr):
-            return arr[0]
-
-    class _MatImpl(_MatrixEntriesInitializer):
-        def pyscope(self, arr):
-            return [list(row) for row in arr]
-
-        def _get_entry_to_infer(self, arr):
-            return arr[0][0]
-
-    return _MatImpl() if is_matrix else _VecImpl()
-
-
 @_gen_swizzles
 class Matrix(TaichiOperations):
     """The matrix class.
@@ -346,13 +324,16 @@ def __init__(self, arr, dt=None, ndim=None):
                 is_matrix = isinstance(arr[0],
                                        Iterable) and not is_vector(self)
                 self.ndim = 2 if is_matrix else 1
-            initializer = _make_entries_initializer(is_matrix)
-            if not is_matrix and isinstance(arr[0], Iterable):
-                flattened = []
-                for row in arr:
-                    flattened += row
-                arr = flattened
-            mat = initializer.pyscope(arr)
+
+            if is_matrix:
+                mat = [list(row) for row in arr]
+            else:
+                if isinstance(arr[0], Iterable):
+                    flattened = []
+                    for row in arr:
+                        flattened += row
+                    arr = flattened
+                mat = [[x] for x in arr]
 
         self.n, self.m = len(mat), 1
         if len(mat) > 0:
diff --git a/taichi/python/export_lang.cpp b/taichi/python/export_lang.cpp
index c25fa95de7134..c187983f0421a 100644
--- a/taichi/python/export_lang.cpp
+++ b/taichi/python/export_lang.cpp
@@ -1138,6 +1138,8 @@ void export_lang(py::module &m) {
 
   py::class_<Type>(m, "Type").def("to_string", &Type::to_string);
 
+  m.def("promoted_type", promoted_type);
+
   // Note that it is important to specify py::return_value_policy::reference for
   // the factory methods, otherwise pybind11 will delete the Types owned by
   // TypeFactory on Python-scope pointer destruction.
diff --git a/tests/python/test_matrix.py b/tests/python/test_matrix.py
index 54aaa1cc81ff2..2b21f0f3501b2 100644
--- a/tests/python/test_matrix.py
+++ b/tests/python/test_matrix.py
@@ -1205,3 +1205,13 @@ def foo() -> ti.types.vector(4, ti.i32):
         return ti.Vector([a[0, 0], a[0, 1], a[1, 0], a[1, 1]])
 
     assert (foo() == [1, 2, 3, 4]).all()
+
+
+@test_utils.test(debug=True)
+def test_matrix_type_inference():
+    @ti.kernel
+    def foo():
+        a = ti.Vector([1, 2.5])[1]  # should be f32 instead of i32
+        assert a == 2.5
+
+    foo()