In this paper, an active calibration method using four active radar calibrators is presented based on the calibration requirements of the precipitation radar. The layout of the active radar calibrators is given, and the timing of the active calibration is designed. The sources of errors in the calibration process and its influence on the calibration accuracy are analyzed. The simulation results show that the calibration accuracy of the radar beam matching is better than 0.01°, and the calibration accuracy is better than 1 dB. While satisfying high-precision calibration requirements, this method can evaluate the performance of the radar in the precipitation observation mode, and reduce the complexity of the calibration experiment.