A three-dimensional inverse design of a submersible axial-flow pump was performed and the loading distributions of both the impeller and guide vane were studied. The hydraulic efficiency was set as the design objective, the optimized loading distributions of the impeller and the guide vane were attained based on numerical simulation results. The orthogonal experimental design, univariate analysis and the numerical simulation were used to study the influence of the loading distribution parameters on both the flow characteristics and hydraulic performance of the submersible axial-flow pump. In order to get superior hydraulic efficiency, the impeller should be fore loaded on both the hub and the shroud, and the guide vane should be mid loaded for the hub and fore loaded for the shroud. Specifically, the range of the loading parameters were as follows: for the impeller blades, the loading slope was in the range of -1~0, which was a front loaded kind, the front loading point was in the range of 0.25~0.45, and the after loading point was in the range of 0.55~0.75;for the guide vane, the hub slope was close to 0 which was a mid loaded kind, the shroud slope was ranged from 0 to 0.75 which was after loaded kind, the hub front loading point was in the range of 0.25~0.45, the shroud front loaded point was close to 0.25, the hub after loading point was in the range of 0.55~0.75. In the impeller design, it was found that the front loaded blade can suppress secondary flows in the blade outlet near the hub. Due to the diffusion structure of the guide vane, the seperation vortex near the wall was inclined to happen. In the design of guide vane, it was found that the separation vortex near the wall was suppressed in the hub-mid-loaded and shroud-fore-loaded diffuser. The impeller and guide vane with the above loading distributions were matched with each other, which can give a better design outcome for the submersible axial-flow pump.