The function of the hydraulic cylinder is to convert the pressure of the tap water system into the power of mechanical equipment.The hydraulic cylinder takes tap water as the working medium and should adapt to the characteristics of high corrosivity and weak lubrication ability of tap water.Using 6061 alloy as the cylinder block manufacturing material,the piston was sealed with Y-type TPU sealing ring.A double cavity lubrication device was designed in the cylinder body to lubricate the piston and piston rod.Through the calculation and verification of structural parameters and prototype test,the thrust and structural strength of the hydraulic cylinder meet the design requirements,the sealing and lubrication effect of the piston is good,and the operation is smooth.The structure of the hydraulic cylinder provides a reference for the design of other water hydraulic equipment with tap water as the working medium.