Abstract：The relationship between wave velocity and load in a pillar，and corresponding relationship between fracture zone and wave velocity distribution are analyzed. The fuzziness of wave velocity and stability of a pillar is also discussed. Furthermore，fuzzy reasoning system is established using fuzzy mathematical theory. In the system，rock integrality coefficients are used as input variables and stability of pillar and possibility of partial failure of pillar are used as two output variables. The system is applied to Suichang Gold Mine in Zhejiang province and good results are obtained even if measurement points are not enough.
