The mixed flow pump is between the centrifugal pump and the axial flow pump in appearance and structure. The liquid in the mixed flow pump flows out of the impeller obliquely, that is, the flow direction of the liquid has both radial speed and axial speed relative to the impeller. The performance of the mixed flow pump is lower than that of the centrifugal pump, but the flow rate is higher; compared with the axial flow pump, the head is higher and the flow rate is smaller. The shape of the performance curve of the mixed flow pump is also between the centrifugal pump and the axial flow pump. For the high-lift mixed flow pump, the relationship between the flow rate and the head, the flow rate and the power is close to the centrifugal pump. In use, the valve can be closed start up. For low-lift mixed-flow pumps, the variation between performance parameters is close to that of axial-flow pumps. It is not appropriate to use valve-closing start, but should start with valve open. At this time, the power is relatively small, and the motor is not easy to be burned. The mixed flow pump can be divided into two types: volute type and guide vane type according to its structural type. There are two types of volute mixed-flow pumps, horizontal and vertical. At present, the horizontal type is widely used in production and use. The vertical type is mostly used for large pumps. The structure of the volute mixed-flow pump is similar to the single-stage single-suction centrifugal pump. Guide vane mixed flow pump is similar in shape and structure to axial flow pump, and is divided into horizontal and vertical