Abstract：According to the viewpoint of discontinuity control and structure breakthrough of rockmass stability，the stability of rock slope engineering is greatly controlled by the distribution and stability state of key block system which is formed by the combination of rock discontinuities with excavation plane，so it is very important to determine and control the stability of key block system. For a complex high rock slope engineering as example，based on the analysis of geological conditions for the slope，especially the distribution of rock discontinuities，the distribution laws of block system for the complex rock slope engineering are analyzed by key block body theory firstly. Then the location，scale and stability coefficient of key block system of the complex slope are found out and calculated，and above results are used to instruct and optimize the monitoring layout in field，so that the correct bolt support is made effectively according to the monitoring information of key block system.
