Taking the PTFE lip seal used in one typical engine as the research subject,the leakage failure when the PTFE lip seal was tested under high temperature and sliding speed was investigated,and the systemic analysis was carried out from the aspects such as material,structure,speed and wear.The results show that the main failure reasons of PTFE lip seal are deteriorated creep of PTFE under high temperature,and the decrease of resilience of PTFE lip owing to the heat induced by high speed and high environment temperature.Meanwhile,the rebound resilience of PTFE and radial force and the selfcompensating ability are decreased,which cause the seal failure.The failure reason of the sealing ring was also discussed from the aspects of interference of the sealing ring.It is found that the radial force and resilience of the sealing ring are decreased under high temperature.The problem of leakage under high temperature can be solved by adjusting the amount of interference to realize the selfcompensating ability.