To explore the medication regularity of prescriptions against diarrhea in The Chinese Medical Code based on Traditional Chinese Medicine Inheritance Support System(TCMISS) to provide new ideas and methods for the clinical treatment of diarrhea by TCM and new drug development.Methods:Oral prescriptions for the treatment of diarrhea in The Chinese Medical Code were collected.A database of ancient literature on the treatment of diarrhea was established.TCMISS was employed to analyze the frequency of drug use，qi，flavor，meridian tropism，and formulation regularity of the screened prescriptions.Results:A total of 427 prescriptions were screened out，involving 358 Chinese herbal drugs.There were 13 Chinese herbal drugs with frequency≥43 times，and the top 5 drugs were Glycyrrhizae Radix et Rhizoma，Coptidis Rhizoma，Zingiberis Rhizoma，Angelicae Sinensis Radix，and Ginseng Radix et Rhizoma.The most commonly used drugs were deficiency-tonifying ones.In terms of drug nature，the majority of drugs were warm，followed by cold and neutral.In terms of flavor，the drugs were mainly bitter，followed by sweet and pungent.The drugs mainly acted on the spleen and stomach meridians.Zingiberis Rhizoma-Glycyrrhizae Radix et Rhizoma served as the most common drug pair.The prescriptions with core combinations of Coptidis Rhizoma，Phellodendri Chinensis Cortex，and Asini Corii Colla were abundant.Conclusion:The medication against diarrhea by ancient doctors is characterized by the combination of cold and warm drugs，and the treatment methods are dominated by both clearing and tonifying.