Abstract: Evolutionary algorithm and HFSS-MATLAB-API were applied to the optimization of microstrip antenna, and detailed steps of the scheme were also displayed together with some common problems which appeared in the process of optimization, such as the definition of gene sequences, individual fitness value derived from evolutionary algorithm combined with high frequency structure simulator-matrix laboratory-application programming interface(HFSS-MATLAB-API), design of fitness function and consideration of genetic strategies etc. Finally, the frequency reconfigurable microstrip antenna was obtained, which can work dynamically at S band or X band via the closing and opening of switch.