Taking the O-shaped rubber ring in the reciprocating seal of the Hydraulic cylinder as the research object, a two-dimensional axisymmetric model was established. With a friction coefficient of 0.1, different medium pressures and different pre-compression ratios, the finite element software ANSYS workbench is used to analyze the deformation and stress of the O-ring during installation, static pressure and working conditions. The results indicate that: when the compression rate exceeds 15% during reciprocating motion, it is easy to cause O-ring stress relaxation, compression permanent deformation, and loss of sealing ability; and the seal ring has the most obvious stress concentration in the gap between the cylinder and the piston rod. In this position, it is easy to be squeezed into the gap, causing gap bite, resulting in seal failure; in the case of oil pressure less than 15MPa, the shear stress is always less than the shear strength of nitrile rubber, but under the reciprocating movement, the sealing ring will continue to It is easy to accumulate damage by friction and wear, leading to cracks or damage.