Aimed at the wedged ring connection and seal structure of the Magnesium alloy cylindrical cabins for an unmanned underwater vehicle，the selecting of the O-ring sealing materials in the connection place, and the lubricating greases used in the seal ring surface was analyzed and compared.By the experiments of tightness and compatibility，the tightness performance of selected rubber seal and the compatibility of selected lubricating grease with rubber seal rings were investigated．The results show that EPDM rubber seal ring has best air tightness for the wedged ring connection structure, and the 7608 synthetic lubricating grease of hydraulic system has excellent compatibility with the EPDM rubber seal ring.