Abstract：The safety and stability problems of high rock slope，such as weaken massif，fully developed geological conformations，widely unloaded or flabby rock layer，and squirming or sliding rock，are often encountered in engineering practice. So，it is very important to enforce the high slope rock deformation monitoring，and to process and analyze the measuring data timely. The high slope of the left bank of Lijiaxia arch dam is given as an example to search the method of how to analyze and evaluate the safety performance of high slope by utilizing rock deformation monitoring data. Based on space-time qualitative analyses of the dam-site valley breadth，slope rock deformation monitoring data measured after the first reservoir impounding，and physical genesis analysis of doubtful rock deformation points，the progressive regression models of rock deformation survey points were set up by using the least-square method；and the results of model simulation and partition to the variational extension of annual deformation of all surveying points were utilized to analyze the influencing effects of the independent variable factors such as hydraulic pressure，temperature and time-effect related to the high slope rock deformation. The conclusions obtained from synthetical analysis of the deformation monitoring data of the left bank of Lijiaxia arch dam are as follows：(1) the high slope rock principally slided downwards the riverbed during the period of impounding water being escalated to normal reservoir level；(2) the rock deformation of the high slope gradually tended to converge and keep stable after January，2002，when the impounding water rose to normal reservoir level，and now the safety performance of the left bank is normal；and (3) presently，part of the left bank rock still tends to slide downwards slightly. So, a suggestion is proposed to strengthen the safety monitoring.
