The precision of time discrimination module is the main influence factor for the range resolution of pulse laser 3D imaging system,and the selection of time discrimination methods has an important significance for system design.Some typical methods of time discrimination in the Simulink were realized,such as frontier threshold,CFD and CR-high pass time discrimination.Combined with simulation of laser echo,the errors of CFD and CR-high pass time discrimination were analyzed under the conditions of pulse width from 0.1～10 ns,incidence angle from 50°to 90°and target distance from 0.1～10 km.Simulation results show that the error of CR-high pass time discrimination is better than that of CFD.Comparing with statistical analysis,this method can dynamically show the errors of various time discrimination methods under different circumstances based on laser waveform feature and circuit characteristics,which provides a reference for the selection of time discrimination methods in the practical application.