Abstract: In the stochastic user equilibrium assignment model of transportation analysis, the assumption of independent and identical distribution (IID) was the reason for simplifying calculation while it is the fatal weakness as well. Aimed at this problem, an assignment model considering the interaction between alternatives in the choice set was proposed. This model introduced the commonality factor into the deterministic part of the utility function to capture the degree of similarity between the alternatives. And the uniqueness and equivalence conditions of the proposed model were proved by mathematical derivation. Moreover, the model was established by the method of successive average (MSA). Finally, network in Beijing Olympic Park was chosen as the trial plot to validate this method by the platform of VISUM. The assignment results of proposed model and traditional UE model were compared. The results indicated this model makes flows distributed more evenly between paths, which might be more close to practical situation.