Task allocation is crucial to improve the efficiency when UUV performs large-scale searching tasks. In this paper，task allocation problem of UUV swarm in multi-area searching is solved to minimized the completion time of area searching. Aiming at the problem that the traditional Hungarian algorithm cannot solve the problem of unbalanced task allocation，an improved Hungarian multi-round allocation algorithm is proposed. This algorithm achieves efficient utilization of idle UUVs and reasonable allocation of target areas through multi-round task allocation. By introducing marginal cost and conservative estimated time in the cost function，the completion time of area searching is greatly reduced. Simulation results show that the algorithm proposed in this article can be used to allocate idle UUVs and improve allocation efficiency compared with the traditional Hungarian algorithm. In addition，compared with the algorithm only using the search time as the cost function，our algorithm can shorten search time as much as possible for long-time-consuming areas，ensuring that the completion time of area searching decreases monotonically as the number of UUVs increases.
