In order to study the influence of the impeller back blades on the external characteristic parameters, axial force and internal flow field characteristics of slurry pump, a 150ZJ-I-C42 slurry pump was taken as a research object. Firstly, the 3 full-flow channel calculation model including the suction chamber, impeller, volute case, extended inlet and outlet parts were established. Secondly, based on CFD numerical simulation technology, steady simulations of slurry pump with and without back blades were carried out under six different operating conditions. Finally, the simulation results were analyzed and compared with the experimental data. The influence of back blades on slurry pump’s performance, pump chamber pressure and axial force was obtained. The results show that, the head and input power of slurry pump with back blades increase obviously, but the efficiency decreases. When the impeller applying back blades, the pressure difference value between the impeller’s front and rear cover plates greatly decreases, which results in a much smaller value of axial force. As the flow rate increases, the axial force direction will change, and the effect of the back blades balancing the axial force will be more significant. The Numerical calculation results are quite similar to the experimental data, which showing high reliability. The results of this research can provide some advices for the operation and optimization design of slurry pump.