A high integrity pressure protection system(HIPPS) is a kind of safety system to prevent over pressurization of onshore and offshore plant. The role of HIPPS is to shut off the source of the high pressure rapidly before exceeding design pressure of a system, therefore important equipment linked on pipe line can be protected by high pressure. HIPPS is consist of three parts, sensors to detect the high pressure, a logic solver to process input pressure from sensors and final elements to perform actual shutting off action to the source of overpressure. The main devices of final element are valve and actuator, and performance of actuator is very important for rapid response of HIPPS. The actuator must have high structural reliability to maintain the performance under rapid shutting off motion. This study address the evaluation and improvement of structural stability of actuator design by using finite element method(FEM).