This paper examines a typical gneiss forming the foundation Xiaowan Hydropower Station. Grinding test is used to analyze the formation environment and mineral composition of the biotite granite gneiss. The results confirm the relationship of the rock strength with its mineral content and mineral strength. Furthermore, acoustic emission is carried out during the uniaxial compression tests of the biotite granite gneiss samples. The acoustic emission process is examined during the biotite granite gneiss instability and rupture. The AE results are used to analyze the crack propagation with time, stress and strain. The results are meaningful for the analysis of rock fracture instability mechanism.