Aluminum alloy has been proposed as one of the next generation of lightweight body structure materials, which is widely used in the main components of the aerospace field. In order to realize efficient and accurate forming of aluminum alloy cylindrical parts, the response surface method combined with finite element simulation was used to optimize the key processing parameters during the hydromechanical deep drawing process. Three processing parameters of friction coefficient, pressure rate, and fillet radius of the die were selected as the optimization variables, and the maximum thinning rate of cylindrical parts was selected as the optimization evaluation index. The Box–Behnken design was selected to design the experiment scheme. A quadratic response model between the maximum thinning rate and the processing parameters was established by the response surface analysis software Design Expert for experimental design and data analysis. The optimal processing parameter combination was obtained through this model. The results show that the optimal conditions of maximum thinning rate can be met when the pressure rate is 11.6 MPa/s, the friction coefficient is 0.15, and the fillet radius of the die is 8 mm. Finally, the experimental verification was carried out by using the optimized combination of process parameters. It was found that the error between the experimental results and the predicted simulation results was within 5%, and the cylindrical parts which met the quality requirements were finally formed.