Abstract: Focusing on the tracking problem of multi-target hidden in AEW (airborne early warning) radar DBZ(Doppler blind zone), a collaborative tracking technique between AEW and ground-based radar was proposed based on IMM, distributed UKF and JPDA. The dynamic fusion weights were calculated for all radars and the Doppler frequency of each target was predicted in real time using target state estimation and prediction. On one hand, as long as the target measurements of AEW radar did not exist and the target was hidden in DBZ of AEW radar judged from its predicted Doppler frequency, targets state would be extrapolated by AEW radar, which creates virtual measurements. The target fusion state estimation would be updated by both virtual measurements of AEW radar and real measurements of ground-based radar. On the other hand, when the targets measurement of AEW radar did not exist and the target was not hidden in DBZ of AEW radar judged from its predicted Doppler frequency, the targets fusion state will be updated by ground-based radar all alone. After the target fly off the DBZ, the target state estimation of AEW radar will be associated with that of ground-based radar again. And the targets fusion state will be updated by both AEW radar and ground-based radar according to the dynamic weights. Simulation results show that the presented method can improve the continuity and accuracy of multi-target tracking in DBZ.