Time discrimination circuit is an important part of lidar. It is used to detect the termination time of the echo pulse signal reaching the receiver and inform the processor for data processing. In order to meet the requirements of lidar system for accurate time identification of time identification circuit, this paper uses the differentially amplified echo pulse signal to perform differential level shift and sends the shifted differential signal to the high-speed comparator for time discrimination, realizing the function of time discrimination. Through verification, the design can effectively improve the walking error caused by the front-line time identification method, which also improves the ranging accuracy. Compared with the constant ratio timing identification circuit, the circuit is simplified.