Abstract: An adaptive fusion algorithm based on time window is proposed for distributed detection of underwater acoustic signal under communication constraints,such as large propagation delay and low reliability in underwater acoustic sensor networks.Each sensor node makes a local decision according to the characteristics of sonar receiver and sends it to the fusion center node.Within the time window,this node adjusts the decision rule on line based on the received local decisions.Thus,a final decision is made according to the optimal fusion algorithm.The selection of time window,as well as the algorithm performance is further discussed by simulation.Simulation results show that the new algorithm is highly practical,and systems with the proposed algorithm can function effectively in dynamically variational underwater acoustic communication.