Aimed at the problem of high temperature sealing for a certain type of product acceptance test (medium maximum〖JP+2〗 temperature of 300 ℃), a new type of hightemperature sealing device was designed based on the original test 〖JP〗equipment. The device was mainly composed of mounts,up/down clamping screw cap and sealing ring.The sealing ring was the key part，which was made of a new special modified PTFE material that can withstand a temperature of 320 ℃. The designed high temperature sealing device was proved to have a good hightemperature sealing effect by practice test.