In order to solve low boring efficiency of TBM caused by geological conditions, the TBM boring performance parameters estimation based on rock mass rating (RMR) system is proposed in view of TBM data base of Songhua River Water Conveyance Project in Jilin Province. The empirical correlation formulas of RMR with TBM performance parameters, i.e. penetration rate (PR), advance rate (AR), utilization (U) and field penetration index (FPI) are respectively given by regression analysis. The study results show that: 1) The relationship between RMR and PR and that between AR and U can be approximated by seconddegree polynomial curves; RMR and FPI present linear relationship, and the correlation coefficients are all larger than 0.7. 2) Better performance of TBM can be reached in fair rock (RMR=50-70) whilst bad performance of TBM will be reached in bad rocks (RMR<30-40) or rock beyond good (RMR > 70-80). 3) The utilization of TBM used in Songhua River Water Conveyance Project in Jilin Province is 22.36%, and geology and rock mass related downtime takes about 25.97% in total construction schedule.