Packer in borehole

The utility model discloses a packer used for pressure cracking an oil well or a water well in the oil field, solving the technical problem that the pipe column is easy to be blocked during pressure crack construction due to the 'high sand rate and low replacement and squeeze', and characterized in the following points: the packer is provided with a recoil sand washing path, composed by a sealing sleeve 12, a well washing valve 9, a pressure cap 10, a bearing head 13, a liner tube 2, a central tube 17, a throw-out collar 19 and a connecting sleeve 20; three hydraulic cylinders have the same structure, comprising a piston bush 26, a link ring 25, a fixed piston 23, a piston 21 and a fixing pin 22; the central tube 17 is a long tube. The packer is used in the pressure crack construction of enclosed well and has the advantages of safe construction and convenient frame assembling and teardown.