In order to study the work principle and the energy conversion mechanism of the impeller of screw centrifugal pump, the screw centrifugal pump of type 100 LN-7 is simulated by using the theory of computational fluid mechanics. Thus, the parameter of velocity on impeller domain of screw centrifugal pump is obtained. On the basis of introduction of the head movement and the load factor, experimental program is established through expressing Euler equation with velocity. With the theory of the airfoil blade loading, Euler equation is used to connect the energy conversion of screw centrifugal pump with the geometric shapes and the size of impeller. The energy change along the angle of impeller is analyzed to reveal the energy conversion characteristics on impeller domain of screw centrifugal pump. The results show that the energy transfer is provided by the propulsion function of screw segment while the energy conversion is accomplished by centrifugal section. The two parts cooperate with each other and make up the working process of screw centrifugal pump. In particular, the lift of blade airfoil loading leaves the largest contribution to the work, which has the vital significance for improving the hydraulic design of the impeller of screw centrifugal pump.