Abstract: In order to explain the influence of the starting and ending positions of the partition and their matching relationship on the radial force and the hydraulic characteristics of the centrifugal pump, six research schemes were proposed, and the full channel steady-state simulation was carried out for each scheme with the help of CFX simulation software. Then, the internal flow state of the centrifugal pump, the hydraulic characteristics of the unit and the radial force parameters were obtained. In order to verify the accuracy of the calculation, hydraulic performance tests of some schemes were conducted. The results show that: for the optimal model, the starting position of the partition and the tongue are separated by 180°, and the ending position of the partition and the starting position are in the same radial plane, and this model can take into account the hydraulic characteristics and radial force characteristics of the centrifugal pump. Since the hydraulic characteristics of the centrifugal pump are not sensitive to the starting position of the partition, based on the starting position of the ideal partition model, the angle between the starting point of the partition and the tongue is increased by an additional 30°, and the maximum change of the hydraulic characteristics is less than 2%. The length of the partition increases as the ending position of the partition moving to the outlet of the volute. This has a certain rectification effect on the internal flow pattern of the centrifugal pump under small flow conditions, resulting in the hydraulic characteristic becoming better for small flow conditions and worse for large flow conditions, while the hydraulic characteristic curve shape tends to be steep. When the starting and ending positions of the partition plate deviate from the optimal model, the radial balance capacity of the volute decreases, but it is better than that of the single volute. The research results can provide a reference for solving the problem of small-base circular volutes, which is difficult to achieve the double-volute design due to the narrow space.