Abstract: In order to seal the hydraulic oil in the transmission, a piston ring with C-type cut was designed. To provide a guide for dimension design, a dynamic stress analysis was simulated for the designed piston ring by the ABAQUS software. Meanwhile, a metal gauges with groove was designed to help the measurement of the size of piston ring. Finally, a practical test was carried out for the piston ring by customers. The test results indicated that the piston ring designed by this work could meet the requirements for transmission sealing. On the other hand, this test also confirmed that the analysis software used in this work could well serve for the design of sealing rings.