The traditional method of fault diagnosis is mainly based on the analysis of the vibration, whichhas great limitations in some special circumstances, but the method based on the sound signal from the equipment in the process can solve the problem. A new method for fault diagnosis based on L type acoustic array is presented in this paper. The DOA estimation based on twodimensional MUSIC is used in radar, and the performance of the algorithm is studied.And with three kinds of different parameterson 2DDOA estimation, the computation is carried out.The comparison with the result of the rectangular arraysis carried out.The resultsshowthat the corresponding algorithm performance is changed while the different parameters have different values.And the method with suitable parameters could be better for the fault diagnosis of the gear drive system.