The utility model discloses an engine gas tightness detects positioning and clamping device. The utility model provides a: an engine gas tightness detects positioning and clamping device, is includingsupporting bench, prop up the elevating system that supporting bench includes PMKD and is located the PMKD top, the last dismantlement of PMKD is provided with two reference columns, be provided withpressure sensor on two reference columns, pressure sensor is connected with the speaker, be provided with the tight unit of first clamp around the PMKD, the last second that is provided with of elevating system presss from both sides tight unit, tight unit of first clamp and second press from both sides tight unit and all include a plurality of push -pull air cylinder, the last gas absorption mechanism that is provided with of elevating system, gas absorption mechanism includes a plurality of through -hole. The utility model provides a scheme positional accuracy is high, can improve work efficiency and reduce the pollution to the engine.