Abstract: A new planar ultra-wideband antenna was designed, using genetic algorithm combined with finite difference time domain method, by which searching for a plannar microstrip antenna locally. Voltage standing wave ratio of the antenna was less than 2 in 3 ~11GHz which met index requirements of the FCC rules. The proposed antenna was fabricated and tested. Measured results, CST simulation results and numerical results were basically consistent and met the design requirements. Antenna radiation pattern and gain characteristics were analyzed. The results show that the design method of the antenna is correct and effective. Compared with global search, it improves design effenciency. The performance of the designed antenna, with high practical value, is excellent.