The most common used method for safe monitor of high slope is to set a fixed observation point to monitor the transformation. But in urban area, due to restriction of the site and telecommunication conditions the transformation of high slope may have an impact to the fixed point and the result and the result we take from the point may be not correct. To avoid the impact and improve the accuracy, in this paper, a coordinate difference method to monitor the transformation of high slope with Total station actively is put forward and the principle, error analyses of this method are described and its application in safe monitor of high slope is introduced.