Abstract: Valve chambers and gas transmission stations of long-distance pipelines are equipped with trunk block valves. These valves, in conjunction with gas-hydraulic actuators, facilitate trunk line isolation during accidents. However, abnormal shutdowns frequently occur during daily operations, posing significant risks to production. The analysis of the automatic valve closing mechanism of gas-hydraulic actuators identified several factors contributing to abnormal shutdowns of trunk block valves. These included issues with the electronic control unit, solenoid valve, and pilot valve, as well as human factors. Specifically, the electronic control unit might experience insufficient battery voltage, high current interference from lightning strikes, and component aging. The solenoid valve might suffer from internal leakage and power loss in the ESD solenoid valve, while the pilot valve was prone to internal leakage. Human factors included inadequate inspections, misoperations, and insufficient maintenance. The specific causes of these factors were further analyzed, and corresponding preventive measures were proposed to ensure the normal operation of trunk block valves in long-distance pipelines.