Abstract: Two typical oil injection failures of the same type occurred to 10726-S pneumatic-hydraulic actuators during production and operation. In order to better promote the development of the regional management mode of oil/gas pipelines and stations and improve the capability of the operators to treat failures of imported equipment, deep analysis was conducted to the functions of the main components of the 10726-s actuators, the operating principle of the gas circuit under normal conditions, and the operating principle of the gas circuit in performing the command of station ESD system for valve shutdown, so as to find out the root causes of oil injection failure. With reference to the operation status and the daily maintenance of field equipment, specific solutions and effective preventive measures were put forward to ensure the safe and stable operation of the equipment. Thus, the research results could provide theoretical basis for judging the causes of various faults and the maintenance treatment methods of various failures of the Shafer pneumatic-hydraulic actuator and they are also helpful to enhance the fault treatment capability of the operation and maintenance staffs.