In order to analyze the reciprocating seal performance of Oring in hydraulic cartridge valve under the deepsea special environment，the twodimensional model of Oring reciprocating seal structure was created based on the ANSYS software. The friction and contact stress of Oring for different conditions and the stress changes in the process of reciprocating motion were analyzed. The result shows that the Oring can realize reciprocating seal performance for different conditions under deepsea.The stress changing at the beginning of reciprocating motion, then tends to be stable.The high pressure of deep sea environment has little influence on the Oring sealing performance and it can be neglected.