In order to make rational use of port resources and reduce the malicious competition between ports,this paper presents a method for the study of the evolution law of port groups based on the rank-size rule.This method uses throughput as an index to measure port scale,and adopts variation coefficients and Gini coefficients to study the difference of regional port group scale.Besides,the primacy index is used to determine whether the regional port group obeys the rank-size distribution.Then,the rank-size rule is applied to study the scale distribution of regional port groups and quantitatively analyze development and evolution law of regional port group.Finally,we choose the EU ports group as a case study.The results indicate that the size of the EU port group is quite different and the degree of imbalance will increase year by year;the EU port group conforms to the rank-size rule,and the throughput growth rate will decrease with the ports rank from high to low.