The speed control system for high power variable speed hydraulic coupling is studied

and the importance of the speed regulation characteristic linearization is pointed out.The mathematical model of speed ratio

the displacement of scoop tube

working oil and inlet area is set up

and the corresponding relation of speed ratio

working oil and inlet area is obtained.A design method of inlet&outlet compound regulating speed system is given

and the design method of oil inlet shape of valve and groove shape of scoop tube are introduced.