High power resonant transducers made with 1-3 piezocomposites are widely used in Non Destructive Testing (NDT) for industry and ultrasonic medical devices. A new nonlinear characterization method with burst excitation, in similar conditions to those in air-transducer applications, is proposed. It measures both the current flowing and the vibration velocity in the piezocomposite transducers, just before the end of the burst signal excitation, near the thickness resonance frequency for different piezocomposites. Three amplitude level dependencies have been studied: a) mechanical loss tangent tan i m , b) the stiffness variations j c / c 0 and c) the ratio between velocity and current. This method allows us to characterize accurately the nonlinearity of piezocomposites as well as ceramics of low or high mechanical quality factor, avoiding the overheating of the transducer.