The time-discrimination method determines the measurement accuracy of an entire system in the receiver circuit of a LiDAR (LightLaser Detection and Ranging). As the accuracy of the traditional leading-edge time discrimination method is not high and the constantratio timing method presents considerable device loss, a new time discrimination method is proposed. First, two voltage amplifiers with high and low gains are used in parallel to obtain two pulse-voltage signals with different gains. Subsequently, The front and back edges of the two pulse voltage signals are obtained using the four comparators. Finally, the centroid of the echo pulse is obtained using a geometric averaging algorithm, to determine the arrival time of the echo. MATLAB simulations showed that the accuracy of the proposed method is better than those of traditional methods. The output waveform of the voltage amplifier and comparator conformed to the expected results obtained by simulating the time-discrimination module by employing Multisim. Finally, the time application of the discrimination module designed by the proposed time discrimination method to the receiver revealed that the module satisfied the system accuracy requirements of the 3D imaging LiDAR receiver circuit in experiments, demonstrating a good 3D imaging effect