The utility model relates to a bore hole pump piston is equipped with cap machinery dismouting device. Its technical scheme is: be fixed with the operation panel at the top of support, the middle partof operation panel is equipped with the T -slot to through T -slot installation U -shaped fixture block, support the piston pump main part through the U -shaped fixture block, the periphery of T -slot be fixed with the piston cassette, the one end of piston cassette is uncovered, and the other end is equipped with rights the groove, the left end of operation panel is equipped with a spacer and amotor support ring, and the motor support ring sets up the left end upside at a spacer for support hydraulic motor's output shaft and sleeve, hydraulic motor's power passes through high -voltage tubeand hydraulic pump intercommunication, and hydraulic motor drives the rotatory piston of realizing of special sleeve and is equipped with the dismantlement and the installation of cap. The beneficialeffects are that: realize that the piston is equipped with the mechanized dismouting of cap, replace the manual labor that artifical dismouting piston is equipped with the cap, avoided the phenomenonof colliding with of artifical dismouting in -process, alleviateed intensity of labour, improved work efficiency.