Fluid end structure of reciprocating pump

The invention discloses a fluid end structure of a reciprocating pump. The fluid end structure of the reciprocating pump comprises a supporting main pump body, a valve cavity body fixedly connected with the supporting main pump body and a plunger piston. The plunger piston penetrates the supporting main pump body and stretches into a first cavity of valve set modules. The outer wall of the plungerpiston is sleeved with a main seal box assembly and an auxiliary seal box assembly. The main seal box assembly is arranged between the outer wall of the plunger piston and the supporting main pump body. The auxiliary seal box assembly is arranged between the outer wall of the plunger piston and the main seal box assembly. Lubricating grease is fed into the main seal box assembly and the auxiliaryseal box assembly of the fluid end structure, friction between the plunger piston and packing can be reduced, heat can be reduced, and the service life of the plunger piston and the service life of the packing can be prolonge