The subject of this study is to make an optimum criterion for collision avoidance action deciding by navigator. This criterion can be used for training of collision avoidance and design of a collision avoidance aids. Here, three kinds of decision-making model which considered about a collision risk by multi-targets and an action loss by a deviation of ship's position and by an action change, were made. Then, these models were evaluated by simulation method. The results by the simulation tests showed that it was better for reducing the action loss to have actions of every sort, and it was necessary to consider about a change of targets distribution at decision of own ship's action.