A standard O-ring was selected as the static seal of the cover of hydraulic rotary vane actuator to decrease the cost of manufacture and maintenance. The sealing groove structure and dimension of the cover static seal was optimized to ensure that the static sealing could prevent both external and internal leakage.Through an analytical calculation, the sealing groove size was preliminarily determined,and a finite element model was built for a triple nonlinear finite element analysis(FEA). The deformation and stress distribution of the O-ring in the process of the cover mounting to the stator were simulated by FEA.The anticipated target of the cover static seal was achieved by finite element optimization design.