At the beginning of our research,how to choose a reasonable spatial scale as our basic view is a key issue.Different scales may have the distinct results.The reasonable scale should reflect both the difference and the similarity of the spatial scale.Our research will advance an innovative method start with the hypothesis of spatial stable scale.We think that there is a stable scale,where the system’s exchange of energy and objects are frequently inside the scale,and stable outside the scale.According to these,our aim is to find this scale.Our paper takes residential regions as an example; we think that if people in one block always go out to other places,this means this block has frequent exchange of energy and objects with those places,in this extent,people’s travel frequency can well represent the exchange of energy and objects between one place to other places.Our paper has made a survey about people’s travel frequency,and divided the reasonable distance in theory according to the frequency changes.After compared the distance in theory with those scales in reality like street,blocks,etc,we will get a reasonable spatial scale that mostly matching the one from theory.This scale can be applied into the evaluation about environmental efficiency,spatial government and many other research fields.