A simulation method confirming the approximate phase center of a conical horn feed is proposed for purpose of determining the phase center of the feed of the parabolic antenna. The position of similar phase center of the feed can be found by moving the feed along the axis near the focus of the reflector when the gain of the parabolic antenna is maximal. The simulation model of a rotating parabolic antenna is established，the selected Gauss impulse excitation is illustrated，and the relevant parameters of the feed calculation are analyzed. Six frequency points from 4 GHz to 5 GHz is selected for simulation，and the approximate phase center position corresponding to the frequency points is calculated. The simulation results indicate that the best position of the approximation phase center of the feed is found by simulating the six phase center in all bands. The presented method can provide reference for solving others parabolic antennas.