Research conclusions: The paper proposes the method about the stability detection of Control Points m，which uses the information provided after the early CP Ⅲ plane and elevation control network adjustment and the measured distance and height difference of every two CP Ⅲ points calculated by measured data of free station in fine adjustment of ballastless track，and then compares with known distance and height difference. Theoretical analysis and testing results both validate that the method is correct and can detect the stability of CP Ⅲ points in plane and elevation. So the method proposed in the paper can be widely used in the project.