In this paper, the rotor and the volute of the squirrel-cage fan with dual inlet were optimized to improve its aerodynamic performance. The blade inlet angle, blade exit angle and diameter ratio of the impeller were chosen as optimization variables using the response surface methodology (RSM) to improve the total pressure. Furthermore, another three optimization variables were adopted on the basis of previous optimum results, which are the width of impeller, the location of the impeller annular plate and the location of cutoff respectively. The simulation and experimental results show that the total pressure of the optimal model has been greatly improved without noise increase in comparison with the original model.