To address solving the high dynamics problem of mobile Application Layer Multicast (ALM) nodes,a multicast system's failure recovery strategy in the mobile environment is proposed.This strategy can achieve the goal of quick redirection by using active failure recovery method and the proposed redirection algorithm based on parent node backup.Besides,we propose to use the similarity of multicast tree to measure the impact of the redirection algorithm on the change of multicast system's topology,thus evaluating the quick redirection strategy.S...