Based on the traditional non-destruction ultrasonic testing,the ultrasonic echo signal is decomposed into different parts according to the frequency by using wavelet transform.Through analysis of the welding interface echo and the base face echo within the different bandwidths and combining the influences of different interface type on ultrasonic transmition,the explosive welding plate's interface is discerned.The method of testing the quality of titanium-steel explosive welding plates is concerned. The test conclusion shows that this method is valid for the non-destruction testing of titanium-steel explosive welding plate and has the advantage of convenience,short inspecting periods and non-destruction.