The technique of borehole elasticity modulus method permits to fastly measure the deep rock mass’s mechanical parameters (deformation modulus and elasticity modulus) and to inspect the consolidation effect of rock grouting, so it has irreplaceable advantages. In this paper the borehole elasticity modulus instrument’s structure and measuring principle are presented together with the application results obtained from the the Three Gorges Project. It reveals the efficiency of the technique on the tests of rock mass proper mechanical characteristics, zonation of excabvation unloading and detection of grouting quality.