In practical decision problems, some decision objects may enter or exit the decision system, which will affect the decision results. To deal with dynamic decision problems with uncertain information, we construct a dynamic three-way decision method by exploiting three-way decisions, grey numbers, and grey targets. In this paper, firstly, by considering the similarity of positive and negative bullseye distances, we exploit Topsis, and grey target to construct a conditional probability of three decisions. Then we propose a dynamic update rule based on the changing of the decision objects and determine the object's evaluation function and the threshold's calculation method. Finally, a case is used to verify the effectiveness and feasibility of the proposed model.