Abstract: To deal with the lack of decision-making methods during the evaluation of airflow field on large ships' deck, a relative entropy method for ship airflow evaluation is proposed in this paper. According to the calculation of the airflow field on three foreign ships with the same working condition, the takeoff and landing speed and the change of vortex are presented. Then, the evaluation index of airflow field is built based on these parameters and a decision-making method of entropy theory is introduced to support both group decision and alternatives assessment. The proposed method is proved to be practical and efficient in actual practice.