Abstract: A characteristic medium strength earthquake with 5.9 Magnitude occurred in Heze on Nov.7, 1983 under the background of potential strong earthquake in northern China.This paper provides a comprehensive analysis and investigation on the data of underground fluid in Heze.The earthquake-reflecting ability of underground fluid during Heze earthquake was summarized and the unusual patterns of underground fluid were explored.This study provides robust data for earthquake forecast in the future through monitoring of underground fluid.