The orifice of the hydraulic valve was used to control the flow in the traditional valve controlled hydraulic system, which inevitably led to very large throttling loss. Based on the idea of the digital hydraulic and inspired by the theory that there was no throttling loss in the fully open and fully closed state of the high-speed on-off valve, an innovative configuration of the two-dimensional pulse width modulation rotary valve was proposed to control and distribute the flow of hydraulic system in the way of fluid pulse width modulation, in order to reduce the throttling loss and greatly eliminate the overflow loss through the active overflow. With the rotation of the valve core, the oil could be quickly switched between the high-pressure (the load) branch and the low-pressure (the oil tank) branch, so as to output the discrete flow. And the duty cycle (the ratio of the communication time of the load branch to the total communication time of the oil return branch at a constant speed) was controlled by the axial displacement of the valve core to realize the control of the output average flow. Through the establishment of the mathematical model, the simulation and the experimental research, it was verified that the high frequency two-dimensional pulse width modulation rotary valve can transform the continuous flow of the fluid into discrete and controllable flow. When the output flow of the quantitative pump was 30L/min, the output frequency of the two-dimensional pulse width modulation rotary valve was 200Hz and the control pressure was 13MPa, the output pressure of the two-dimensional rotary valve could be maintained at 21MPa. Taking the duty cycle of 50% as an example, the load flow was about 12.3L/min. This was a flow control method from the perspective of the discretization of the working medium in the fluid system.