Situation assessment of the target is the basis for making military decision in anti-submarine warfare. Through analyzing the antagonistic process between the helicopter formation and the target, and considering the insufficiency and uncertainty of target information in the anti-submarine warfare, we proposed a kind of situation assessment algorithm based on Bayesian network. By establishing an association network between the two sides and the relevant causality and probability tables, we used Bayesian network for ratiocination, and thus to identify the target and its intention. The experiment results showed the validity of the algorithm, which can provide a good reference for military decision-making in anti-submarine warfare by using the target information effectively together with the empirical model for ratiocination and identification.