This paper introduces geology status and safety monit oring design of the left diversion tunnel in construction of Jinping - 1 Hydropower Project simply, expatiates on the results of safety monitoring in construction, and analyzes the rules and characters of stress and deformation of surrounding rock. Now the diversion tunnel has been completed, the changes of deformation and anchor stress for surrounding rock are small. This result shows that the surrounding rock is stable, safety monitoring result can provide reliable basis for design and construction.