In multi-radar data processing system,system error is an important factor for quality of target tracking and data fusion, especially the northern azimuth error with the biggish influence in system. As for the current condition that different radars measure the same target with asynchronous measurement, a method of azimuth registration in asynchronous measurement which adopts Kalman filter was proposed. The method completes the time registration, position and azimuth error estimators together with processing of azimuth registration in time. The simulation results demonstrate feasibility and effectiveness of the algorithm.