Abstract: This paper discusses the inconsistency between the sum and difference channels, which will affect angle measurement if the amplitude-monopulse angle measurement technique is employed. When wide band signal is in use, the channel amplitude and phase property cannot be treated as constants, which, in fact, are variables to frequency. The amplitude and phase imbalances of monopulse sum and different channels are analyzed based on a mathematical model in which amplitude imbalance <14 dB and phase imbalance <0.27 rad. A method of calibrating amplitude and phase imbalances between the two channels is introduced along with the computer simulation results. The results prove that after calibration, the angle measurement's precision is within the system requirement.