In order to deal with the lack of decision method during the evaluation of the airflow field on large ship decks, an initial evaluation index system of the airflow field was built according to the feature of similarity in all parameters. An improved TOPSIS method was proposed by combining the Deng's method and the slope grey relational method. The airflow fields on three foreign ships with same working conditions were simulated. Then, an evaluation method was presented on the basis of the takeoff and landing speeds, the change of vortex and some other related key parameters. With the method, the airflow fields on the three foreign ships were evaluated comprehensively. The results show that the improved TOPSIS method can be applied to assess ship airflow schemes according to the differences between the parameters from the evaluation index system. The present method is effective and feasible to the evaluation of airflow fields on ships.