Abstract: Based on the active element pattern theory (AEP), a rapid method for calculating the time-domain radiation field of pulsed antenna arrays is proposed. With the method, analysis problems of large array are converted into small array problems, and the mutual coupling between elements can be taken into account, so the computational cost is greatly reduced. When the method is combined with electromagnetic software which is based on the finite integral method, we can calculate the pattern of a large array just by simulating a 5×5 array, but the time cost of the method is less then 10 percent of full-wave simulation. The correctness of the method is verified by comparing with the simulation results of electromagnetic software.