Abstract:【Objective】To design a kind of trenching depth control system based on laser sensor,so as to solve the problem that it is difficult to adjust accurately the trenching depth of chain trencher.【Method】The laser triangular-reflecting displacement sensor was used to detect the trenching depth in real time, which was compared with the target value. The closed-loop control of trenching depth was realized by the control system making decision and driving hydraulic system and actuator. The field experiment was conducted to compare the control precision and stability before and after enabling the system.【Result】The result of static test showed that when the different values between the detection depth and the target depth were ±50 mm, the response time of the system were 0.19 and 0.31 s respectively, and the maximum control error was 3 mm. The field test showed that when the trenching depths were 200, 300 and 400 mm respectively at the speed of 3 km·h-1, the control precision and stability for trenching depth of the chain trencher were improved after starting the control system. Compared with closing the system, the control precision and stability coefficients increased by 2.3% and 4.3% respectively after opening the system.【Conclusion】This control system responds quickly with a high control accuracy, and the control error satisfies the set requirements. The result provides a solution for controlling the trenching depth of the chain trencher.