An axial-flow pump impeller is designed on the basis of plane cascade theory, which is based on surface element method, to study the influence of impeller rotor on the hydraulic performance of the a full tubular pump. Then, the performance of the full tubular and axial-flow pumps has been compared and analyzed through CFD and model test, respectively. First, two-dimensional plane cascade theory is used for the hydraulic design of pump impeller blades according to the design condition of an axial-flow pump. Second, the CFD calculations of full tubular pump and axial-flow pumps are performed using numerical simulation software. Finally, the reliability of the numerical simulation is verified by using a model test. Results show that under the design condition of the axial-flow pump, the head, efficiency, and maximum efficiency correspond to 3.30 m, 86.3%, and 86.69%, respectively. In the design condition, the head of the full tubular pump is 3.12 m and decreases by 5.5%, and the hydraulic efficiency is 78.54% and declines by 7.76%. The hydraulic loss caused by clearance backflow and the disc friction loss caused by rotor housing mainly caused the reduction in the hydraulic performance of the full tubular pump. Meanwhile, the decrease in the maximum operating head of the full tubular pump is greater than that of the axial-flow pump. Moreover, the safe and stable operation area of the full tubular pump is only 82.43% of that of the axial-flow pump. This work has important theoretical and guiding significance in the design and practical engineering application of the full tubular pump. • CFD and model test of the axial-flow pump and full tubular pump were carried out, respectively. • The gap backflow and the disc friction loss are the main reasons for the low efficiency. • The gap backflow is mainly affected by the inlet and outlet pressure of the impeller. • The vortex and bias flow phenomenon are observed at the blade inlet of the full tubular pump.