Abstract: To resolve the problem that the low frequency resolution can cause calculation error of ultrasonic nonlinear coefficient, based on the theoretical analysis of the discrete Fourier transform (DFT) calculation process and the influence of the factors such as the length of the truncated length and the amplitude of the waveform on the calculation of the ultrasonic nonlinear parameter, the characteristics of the characteristic data of the excitation signal and the characteristics of the endpoint data calculation method of ultrasonic nonlinear parameter were proposed. The simulation results show that this method can effectively reduce the error of β caused by signal truncation and low frequency resolution, so that the relative ultrasonic nonlinearity parameter of measured signal can be reduced to less than 10% of the standard value.