Abstract: In order to improve the casting performance of differential pressure casting, the A356 aluminum alloy knuckle was used as the research object, the solidification time, the secondary dendrite arms spacing(SDAS)and porosity were used as optimization indicators, and the cooling parameters were optimized through the combination of numerical simulation and optimization algorithms.Firstly, the cooling opening time of different lines was determined as the optimization variable by analysis.Numerical simulation was carried out based on the orthogonal experiment arrangement, the training samples of the support vector machine regression algorithm (SVR) were obtained, and the mapping relationship between the optimization variables and the three optimization indicators was determined; the fish-swarm algorithm was used to find the optimal combination parameters.Finally, the obtained optimal combined parameters were verified by numerical simulations.The results show that the simulation results are basically consistent with the predicted results.Under the optimal cooling parameter combination, the solidification time is reduced from 208.2 s to 175.6 s, the distance between SDAS is changed from 47.25 μm to 44.18 μm, and the porosity is reduced from 12.79%to 0.923%.