The friction characteristics between the rubber cylinder and the oil tube wall significantly impact the service life and drainage performance of the plunger-type robot. This issue poses a critical technical challenge that must be addressed to promote and apply plunger robot technology. This study focuses on investigating the influence of various structural parameters of the rubber cylinder on the sealing performance of the robot cylinder. By employing a simulation approach that integrates fluid-solid coupling within the rubber cylinder structure, we examine the effects. The findings demonstrate that the rubber cylinder with W3G1.5 structural parameters exhibits more even force distribution and lower average contact friction stress.