Abstract: The primary circuit system mathematical model evaluating procedures were compiled, and the effects of thermal and structure parameters on the primary circuit system weight and volume were discussed. The multi-objective optimization of the primary circuit system weight and volume was carried out based on the self-developed hybrid particle swarm optimization. The calculation results show that the total weight and total volume of primary circuit system were reduced by 12.75% and 13.69% respectively after using the optimization strategy, and the optimization effect is obvious.