Aiming to solve the problem that the increase of the size of the radiator is limited by the internal space of the directcurrent (DC) power verification instrument, the global response surface method (GRSM) is used to optimize multiobjectives of the thickness of the substrate and the fins, the number of fins and the airflow. Firstly, a finite element model (FEM) of 1 kW switching power supply is proposed and the orthogonal experiment is designed, with variable factors of substrate thickness H2, fin thickness H3, number of fins N, and fan airflow V, and the objective of the maximum temperature of the power chip and switching power supply. Secondly, based on the experimental results, the multiobjective optimization of the variable factors is conducted by using the GRSM. The results show that the maximal temperature can be decreased to 9161 ℃ and 6273 ℃, respectively, under the conditions of H2=30 mm,H3=10 mm,N=10 and V=2400 CFM. Finally, the experiment is carried out with the optimized parameters, and the experimental results agree well with the optimization ones with marginal errors of -253 ℃ and 370 ℃, respectively. Our scheme presents a significant achievement since the maximum temperature is reduced by nearly 30%, and the obtained optimized parameters are useful.