The traditional operation mode of the injection molding machine is to ensure the “open-loop dosing oil pump”, “asynchronous induction motors” and motor systems are fully operated once switched on. Injection molding process is generally divided into several stages (high pressure clamping, melting plastic, plastic injection, cooling, packing, mold, and thimble). Each stage requires a different operating pressure and flow rate for the pump motor, and difference product requires different settings. The vast majority of existing injection molding machine for the fixed volume pump hydraulic system will provide a constant flow rate, and the excess hydraulic oil will pass through the relief valve reflux, this process is called high-pressure throttling. High pressure throttle generally consists of 60% to 70% efficiency with energy loss of up to 30% to 50%. Meanwhile, the long-term full-speed hydraulic oil circulation, and hydraulic parts, mechanical parts severe great friction, causing the oil temperature too high, producing excessive noise, and shortened mechanical life.