Based on the literature review of medical behaviors, big data mining and related rules, the paper introduces the basic contents of big data mining and related rule algorithm-Apriori algorithm, takes partial Electronic Medical Records(EMR) system data of the First Affiliated Hospital of Zhengzhou University as the basis, conducts mining analysis on factors such as the gender, age, operation records, critical ill records, visiting distance and hospital days of a patient by adopting Apriori algorithm of related rule, obtains the rules of medical behaviors of patients of different visiting distances, and puts forward relevant policies and suggestions.