Hydraulic transmission is a transmission form which uses liquid as working medium, drives the actuator by pressure energy, and drives and controls the energy. Compared with electric drive and mechanical drive, it has the advantages of large output force, light weight, small inertia, stable operation, convenient speed regulation and easy control, and is widely used in many fields such as construction machinery, construction machinery, automated production lines and various machine tools.

Compared with mechanical transmission, hydraulic transmission is a young subject. Since Pascal put forward the principle of hydrostatic transmission in the middle of17th century, and the first hydraulic press was manufactured in Britain at the end of18th century, although hydraulic transmission has a history of 200-300 years, it has not been widely used because of the lack of early technical level and production requirements. With the development of society and the progress of science and technology, the demand for transmission technology is getting higher and higher, which promotes the continuous development of hydraulic transmission technology, especially during and after World War II, which greatly promotes the development and maturity of hydraulic technology due to the stimulation of military and construction needs.