The characteristic of design is that to optimize parameter, appropriately increase stroke and reasonably lower stroke number improve the performance of suctions of pumps. The valve housing of hydraulic end with straight structure is massively forged thus the clearance volume is minimum. The K1:6 conical surface of the valve housing is treated with roll extrusion so the precision of fitting with the valve seat is greatly improved. The water inlet valve is positioned with strongback together with base plate which is convenient and reliable. The holes in the valve housing and the valve seat are machined according to specifications.