A novel real-time robust estimation method based on Kalman filter and data fusion was proposed for error estimation of radar network under multi-target circumstance.Firstly the real-time registration algorithm of Kalman filter was utilized to get the estimated system bias by each target.Then the results were processed by real-time data fusion to make the estimated bias more precise.Simulation results show that real-time error registration under multi-target circumstance can be realized more effectively.