Abstract: The gear structure was handled equivalent to circinal plate,then the dynamics analysis model and acoustical model of fault gear were established,the sound pressure and the distribution characteristic of sound field of gear elastomer with radial direction crack and arc direction crack were analyzed;and the influence of crack on the radiation characteristic of the sound field of gear structure was studied.With the help of ANSYS and MATLAB software,the distribution of sound pressure in the r=0.5m sphere surface and axial sound pressure of cracked gear structure was obtained,and the influences of various crack types and crack sizes on acoustic characteristic of gear vibration were investigated.Based on analysis,comparison and evaluation of the simulation results,it shows the influence extent and rule of the crack location,crack shape and size in relation to acoustic vibration characteristic of gear structure.These lay a good foundation for gear fault diagnosis using acoustic method.