A complete hydraulic system consists of five parts, namely, power components, actuating components, control components and hydraulic oil.

1. The function of power components is to convert the mechanical energy of the prime mover into the pressure energy of the liquid. It refers to the oil pump in the hydraulic system, which provides power to the entire hydraulic system. The structural forms of the hydraulic pump generally include gear pump, vane pump and plunger pump.

2. The function of actuating elements (such as hydraulic cylinder and hydraulic motor) is to convert the pressure energy of liquid into mechanical energy and drive the load to perform linear reciprocating or rotary motion.

3. Control elements (i.e. various hydraulic valves) control and regulate the pressure, flow and direction of liquid in the hydraulic system. According to different control functions, hydraulic valves can be divided into pressure control valves, flow control valves and direction control valves. Pressure control valves are also divided into profit flow valves (safety valves), pressure reducing valves, sequence valves, pressure relays, etc; Flow control valve includes throttle valve, regulating valve, diversion and collection valve, etc; The directional control valve includes check valve, hydraulic control check valve, shuttle valve, directional valve, etc. According to different control modes, the hydraulic valve can be divided into switch type control valve, constant value control valve and proportional control valve.

4. Auxiliary components include oil tank, oil filter, oil pipe and pipe joint, sealing ring, pressure gauge, oil level and oil temperature gauge, etc.

5. Hydraulic oil is the working medium of energy transfer in hydraulic system, which includes various mineral oils, emulsions and synthetic hydraulic oils.