Abstract: During the process of antenna design and optimization, electromagnetic simulation programs usually are of high resource consumption but low computational efficiency. The methodology presented exploits a set of multi-fidelity coarse models with increasing accuracy to approximate the fine model. Fitness function is defined and its optimal solution is searched locally and directionally on each level of coarse model, and then passes to the finer model as the initial design. On the last coarse model, a quadratic model is used for fitting structural parameters and its response vector; then the optimal structural parameter is obtained by traversing solution space. A WLAN dual-band monopole antenna (2.4～2.4835 GHz, 5.15～5.825 GHz) is designed with the proposed method, and the results show that compared with Quasi-Newton method, the optimization time is significantly reduced.