diff --git a/server/config.go b/server/config.go
index cf1b6916847f..54085af6f0f2 100644
--- a/server/config.go
+++ b/server/config.go
@@ -353,15 +353,15 @@ type ScheduleConfig struct {
 	// TolerantSizeRatio is the ratio of buffer size for balance scheduler.
 	TolerantSizeRatio float64 `toml:"tolerant-size-ratio,omitempty" json:"tolerant-size-ratio"`
 	//
-	//     high space stage         transition stage           low space stage
+	//      high space stage         transition stage           low space stage
 	//   |--------------------|-----------------------------|-------------------------|
 	//   ^                    ^                             ^                         ^
-	//   0   (1 - LowSpaceRatio) * capacity       (1 - SpaceRatio) * capacity      capacity
+	//   0       HighSpaceRatio * capacity       LowSpaceRatio * capacity          capacity
 	//
-	// LowSpaceRatio is the lowest available ratio of store which regraded as low space.
+	// LowSpaceRatio is the lowest usage ratio of store which regraded as low space.
 	// When in low space, store region score increases to very large and varies inversely with available size.
 	LowSpaceRatio float64 `toml:"low-space-ratio,omitempty" json:"low-space-ratio"`
-	// HighSpaceRatio is the highest available ratio of store which regraded as high space.
+	// HighSpaceRatio is the highest usage ratio of store which regraded as high space.
 	// High space means there is a lot of spare capacity, and store region score varies directly with used size.
 	HighSpaceRatio float64 `toml:"high-space-ratio,omitempty" json:"high-space-ratio"`
 	// EnableRaftLearner is the option for using AddLearnerNode instead of AddNode
@@ -410,9 +410,9 @@ const (
 	defaultRegionScheduleLimit  = 4
 	defaultReplicaScheduleLimit = 8
 	defaultMergeScheduleLimit   = 8
-	defaultTolerantSizeRatio    = 2.5
-	defaultLowSpaceRatio        = 0.2
-	defaultHighSpaceRatio       = 0.5
+	defaultTolerantSizeRatio    = 5
+	defaultLowSpaceRatio        = 0.8
+	defaultHighSpaceRatio       = 0.6
 )
 
 var defaultSchedulers = SchedulerConfigs{
diff --git a/server/core/store.go b/server/core/store.go
index 47ace78b43d7..8d51bebdcbdf 100644
--- a/server/core/store.go
+++ b/server/core/store.go
@@ -122,17 +122,12 @@ func (s *StoreInfo) RegionScore(highSpaceRatio, lowSpaceRatio float64, delta int
 
 	var score float64
 
-	// lowSpaceRatio shouldn't greater than highSpaceRatio
-	if lowSpaceRatio > highSpaceRatio {
-		lowSpaceRatio = highSpaceRatio
-	}
-
 	// because of rocksdb compression, region size is larger than actual used size
 	amplification := float64(s.RegionSize) / (float64(s.Stats.GetUsedSize()) / (1 << 20))
 
-	if available-float64(delta)/amplification >= highSpaceRatio*capacity || lowSpaceRatio < 0 || lowSpaceRatio > 1 {
+	if available-float64(delta)/amplification >= (1-highSpaceRatio)*capacity {
 		score = float64(s.RegionSize + delta)
-	} else if available-float64(delta)/amplification <= lowSpaceRatio*capacity || highSpaceRatio < 0 || highSpaceRatio > 1 {
+	} else if available-float64(delta)/amplification <= (1-lowSpaceRatio)*capacity {
 		score = maxScore - (available - float64(delta)/amplification)
 	} else {
 		// to make the score function continuous, we use linear function y = k * x + b as transition period
@@ -140,8 +135,8 @@ func (s *StoreInfo) RegionScore(highSpaceRatio, lowSpaceRatio float64, delta int
 		// p1((1-highSpaceRatio)*capacity*amplification, (1-highSpaceRatio)*capacity*amplification) and
 		// p2((1-lowSpaceRatio)*capacity*amplification, maxScore-lowSpaceRatio*capacity)
 		// so k = (y2 - y1) / (x2 - x1)
-		x1, y1 := (1-highSpaceRatio)*capacity*amplification, (1-highSpaceRatio)*capacity*amplification
-		x2, y2 := (1-lowSpaceRatio)*capacity*amplification, maxScore-lowSpaceRatio*capacity
+		x1, y1 := highSpaceRatio*capacity*amplification, highSpaceRatio*capacity*amplification
+		x2, y2 := lowSpaceRatio*capacity*amplification, maxScore-(1-lowSpaceRatio)*capacity
 
 		k := (y2 - y1) / (x2 - x1)
 		b := y1 - k*x1
diff --git a/server/schedule/mockcluster.go b/server/schedule/mockcluster.go
index 796fb7e5df00..b670f755e186 100644
--- a/server/schedule/mockcluster.go
+++ b/server/schedule/mockcluster.go
@@ -379,9 +379,9 @@ const (
 	defaultRegionScheduleLimit  = 4
 	defaultReplicaScheduleLimit = 8
 	defaultMergeScheduleLimit   = 8
-	defaultTolerantSizeRatio    = 2.5
-	defaultLowSpaceRatio        = 0.2
-	defaultHighSpaceRatio       = 0.5
+	defaultTolerantSizeRatio    = 5
+	defaultLowSpaceRatio        = 0.8
+	defaultHighSpaceRatio       = 0.6
 )
 
 // MockSchedulerOptions is a mock of SchedulerOptions