To study the rock classification for the diversion tunnel excavated by Tunnel Boring Machine (TBM), field investigation, data collection and analysis have been done in a hydropower station in southwest China. A regression equation is obtained by multiple regression on the basis of TBM performance parameters and rock strength. The equation is verified by being applied to the geological prediction of different rock classifications. The prediction scores are highly consistent with the field scores. The paper provides a valuable reference for further research on surrounding rock classification of TBM-excavated tunnels.