For the pulse laser detection system using APD circuit, the existing peak extraction method could only detect the linear region of the unsaturated waveform, but not the nonlinear region of the saturated waveform, which made the detection range of the system extremely limited. Therefore, in view of the problem that the current system could not be detected in the nonlinear area, a linear and nonlinear unified response model based on APD circuit was established, and based on the response model, the waveform integration method and the nonlinear area energy inversion model were developed, which could be used to detect the saturated waveform in the nonlinear area, and the ideal inversion fitting of the model to the waveform in the nonlinear area was verified by experiments. The experimental results show that the fitting value had a linear relationship of 1.001 with the actual value, and the maximum relative error of the waveform integration method was only 4.69%, while the detection range was widened to 10.25 times of the peak extraction method, which proved that the method and the model could be used to detect the pulse laser in the non-linear area, and it could be applied to improve the detection range and detection ability of the pulse laser detection system based on APD circuit power.