Because of improving resource utilization and reducing environmental pollution, IPA (Intensive Pond Aquaculture) technology has been widely promoted as a new breed aquaculture technology. In order to improve the efficiency of pollution collection and discharge in the process of aquaculture, the method of constructing negative slope bottom is used to reconstruct aquaculture tanks. By establishing a two-dimensional simplified model of aquaculture tank and combining the CFD-DEM simulation and KPLS (Kernel Partial Least-Squares Regression) modeling method, a model that can reflect the relationship between the vertical velocity distribution and the bottom slope was established. On this basis, the model of the particle incipient velocity and the single wide suspended load transport rate in the tank was obtained by the theory of sediment motion. After setting up two performance indexes of particle motion and transportation, the DP-MOPSO (Preference-based Multi-objective Particle Swarm Optimization) method was used to get the optimal bottom slope. The optimization results show that with the increase of the bottom roughness, the optimal gradient is slightly reduced and the range is about 0.013-0.015. The simulation results show that the optimal bottom slope can effectively improve the moving probability and the transport capacity of particles, and for the rough surface, the superiority of the slope bottom is more significant. It shows that it is reasonable to optimize the discharge performance of aquaculture tanks by constructing the bottom slope to change the flow structure.