System for improving control accuracy of valve and control method of system

The invention discloses a system for improving the control accuracy of a valve. A controller is connected with a flowmeter and an electric valve; a first manual valve is also arranged on a main pipeline between the flowmeter and the electric valve; a second manual valve is arranged on a main pipeline at the lower end of the electric valve; a third manual valve which is connected in parallel with the first manual valve, the electric valve and the second manual valve is arranged on the main pipeline; a fluid input end of the main pipeline is connected with a pressure pump. A control method of the system comprises the following control steps of forming a flow closed loop control system by the electric valve and the flowmeter which is connected in series with the same main pipeline, and moderately opening the manual valve which is connected in parallel with the electric valve to form a coarse adjustment part; comparing the flow which is actually detected by the flowmeter with a set flow in real time and giving an instruction by using the flow closed loop control system, so that the flow is finely adjusted by the actions of closing or opening the electric valve. Through the combination of an automatic control valve and the manual valves, the control accuracy is improved without changing the opening degree of the electric valve each time; the cost is not increased; the system is convenient to control.