In　recent　years,　with　the　acceleration　of　people＇s　pace　of　life,　the　number　of　chronic　diseases　in　China　is　increasing.　The　attention　and　investment　of　the　country　to　the　medical　industry　is　increasing　year　by　year.　At　the　same　time,　with　the　maturity　and　perfection　of　data　mining　technology,　many　countries　have　applied　this　technology　to　the　research　and　mining　of　medical　data.　In　this　paper,　the　Apriori　algorithm　of　data　mining　technology,　and　improve　the　data　format　of　the　Apriori　algorithm　is　applied　to　the　prediction　of　nephropathy,　establish　the　association　rules　between　chronic　disease　and　a　number　of　physical　data　by　the　algorithm,　and　the　experimental　results　proved　that　Apriori　algorithm　is　effective　in　the　medical　data　mining.