Abstract: Using mean effective correlated energy gain (MECG) as the measure parameter of a UWB antenna time-domain performance, and programming with Matlab and CST jointly, this paper applies the genetic algorithm(GA) to rebuild the shape of a UWB planar dipole antenna and achieve the optimal time-domain performance. The optimized antenna has an impedance bandwidth of 3.1 GHz~10.6 GHz, basically meeting the requirements in operation bandwidth of UWB system. The simulated MECG of the new antenna increases by 0.157, and the measured one increases by 0.161.The results of both measure and simulation indicates that the optimized antenna has a good time-domain performance including pulse radiation and pulse fidelity.