In the multi-stage pump chamber eccentric equipped with a trochoid rotor, which along the inner wall of the pump chamber and the pump cavity is divided into two variable volume. Pump dynamic balance is good, so the operation is more stable, the vibration is also small, speed can be increased, you can do small size, pumping speed, suitable for the development of large pumping speed mechanical multi-stage pump. As the suction pipe is short and thick, is conducive to improving the multistage pump pumping speed under low pressure.