Abstract: In order to study the effect of solid concentration on the structure of the circulation flow in the vortex pump,the 150 WX-200-20 vortex pump was taken as the research object. The theory of fluid dynamics and the Eulerian two-fluid model was used. Six mixed fluid of solid and water were used as the flowing medium. The solid concentration was changed from 10% to 35%. Numerical simulation analysis was performed on the vortex pump. The variation rules of the streamline of the flow field in the vortex pump were compared and analyzed. The vortex core positions and shapes of the vortex structure on four 1/4 cross-section arrays with the axis as the center in the pump were studied at different concentrations. The results show that in solid-liquid two-phase flow,a set of main circulation flow I and a set of secondary circulation flow Ⅱ are formed in the vortex pump under the action of the impeller. The main circulation flow transfers the fluid acting at the inlet to form another set of secondary circulation flow Ⅲ. The intervention of solids will weaken the strength of the vortex and inhibit the expansion of the vortex structure area of the cross-section Ⅱ. A flow model of the vortex pump is proposed. With the increase of solid concentration,the variation range of the main circulation flow with the increase of flow in the non-leaf cavity is reduced. Under the operating conditions of the vortex core in the non-leaf cavity,the efficiency increases with the increase of the flow. After the flow increases into the impeller domain,the pump efficiency decreases. At the high efficiency point 1.2 Q_d,the larger the solid concentration,the smaller the distance between the vortex core and the axis. Under the operating conditions of the vortex core in the non-leaf cavity,the value of the shape coefficient of the vortex structure on the cross section is larger at the high efficiency point 1.2 Q_d,and the shape of the vortex structure is relatively flat.