Abstract: The geological conditions are complex in Longtan hydroelectric project. The strata are dipping steeply and the faults are developed. The caverns are constituented with long span and high side wall. So the stability of surrounding rock mass is very important during excavation. In this paper, the excavation and support of caverns are numerical simulated by fast Lagrangian method (FLAC) according to the designer’s scheme. Numerical results of two profiles considering excavation with support are compared and analyzed. Finally some useful conclusions are obtained.