This paper mainly introduces the working principle of throttle valve. Before introducing the principle, let's simply understand what a throttle valve is. Simply put, throttle valve is a structure that regulates fluid pressure, adjusts the amount of air entering the engine and adjusts the output of the engine. What then is the one-way throttle valve in China's Electromechanical industry network? Throttle valves and one-way valves are connected in parallel to form one-way throttle valves. One-way throttle valve is a combination of one-way valve and throttle valve in parallel. Throttle does not work in the direction of the valve. In the opposite direction, the oil can not pass through the check valve, and throttling effect. It is usually used to control the return oil regulation of double-acting cylinders. Throttle valve in China's Electromechanical industry network is a kind of valve that controls the flow of fluid by changing the length of the throttle part or the throttle valve. Throttle valves and one-way throttle valves are simple flow control valves. In the hydraulic system of fixed pump, throttle valve and safety valve cooperate to form three throttle speed control systems, namely throttle valve throttle control system, return oil throttle control system and bypass throttle speed control system.