Abstract： Objective： To analysis the medication rules of Professor LI Fazhi in treating aphtha based on data mining technology. Methods： The clinical records of Professor LI Fazhi in treating aphtha at the Third Affiliated Hospital of Henan University of Traditional Chinese Medicine from January 2015 to October 2022 and the case history recorded by the physicians during their clinical practice and study were collected. The frequency of Chinese medicinals used in the prescriptions，the nature and flavor，and the meridian entries were counted；using R language，the top 32 Chinese medicinals in frequency of use was given the association rules analysis； K-means clustering method was used for Chinese medicinal groups analysis；the proportion of highly-used Chinese medicinals in prescriptions and their meridian entries were subjected to the time-flow analysis. Results： A total of 199 kinds of Chinese medicinals were involved in 1 625 prescriptions，with a total frequency of use of 16 766 times. The frequently-used Chinese medicinals were mostly cold in nature，followed by warm. The frequently-used Chinese medicinals were mainly acrid，sweet and bitter in flavor. The meridian entries were mainly the spleen， lung， stomach and heart. Association rules analysis showed that the medicinal group of Pinelliae Rhizoma Praeparatum cum Alumine， Zingiberis Rhizoma， Coptidis Rhizoma and Glycyrrhizae Radix et Rhizoma was the core， which had the strongest correlation with Schizonepetae Herba and Saposhnikoviae Radix. The top 32 Chinese medicinals in the frequency can be clustered into seven groups. The time-flow analysis showed that Glycyrrhizae Radix et Rhizoma，Scutellariae Radix，Coptidis Rhizoma，Zingiberis Rhizoma and Pinelliae Rhizoma Praeparatum cum Alumine accounted for a higher proportion from 2015 to 2022，and the proportion of Jujubae Fructus and Ginseng Radix et Rhizoma had a significant increase from 2020 to 2022； the medication was concentrated in the meridian entries of the lung and spleen. With the passage of time，the medication of the meridian entries of the stomach，heart and liver was increased，and that of the rest meridian entries was declined. Conclusion：Professor LI Fazhi treats aphtha with the spleen and stomach as the core. The clinical medication focuses on the ascent-descent cause， the combination use of cold and warm Chinese medicinals， and the regulation of the middle energizer. In recent years，special attention has been paid to tonify and boost the middle energizer.