Oryeongsan (五苓散) is a herbal medicine formula that iscomposed of Polyporus, Alismatis Rhizoma, Atractylodis RhizomaAlba, Poria Sclerotium and Cinnamomi Cortex. According toliteratures of traditional oriental medicine, Oryeongsan has efficacyon dispelling dampness. Until now, the most common explanationmethod of medical action of Oryeongsan is the combination effecttheory of the individual herbal medicines. To be specific, Polyporus,Alismatis Rhizoma and Poria Sclerotium have an effect of inducingdiuresis to drain dampness. Atractylodis Rhizoma Alba has aneffect of drying dampness and fortifying the spleen. AndCinnamomi Cortex has an effect of warming the internal body.This explanation method is familiar to the relevant majors butdifficult for non-majors and the general public.For this reason, this study aims to analyze the mechanism ofaction of Oryeongsan using network pharmacology. Chemicalcompounds of Oryeongsan were collected using the TM-MCdatabase which was created by the Korea Institute of OrientalMedicine. In addition, some other compounds and protein targetswere collected through literature review. Protein targets associatedwith the compounds were retrieved from the STITCH database.And related diseases and pathways were collected respectivelyusing DisGeNET database and DAVID tool.As a result of this method, 130 valid compounds and 534 relatedprotein targets were collected. Diseases related to Oryeongsanwere schizophrenia, mammary neoplasms, prostate neoplasms,hypertensive disease, and liver carcinoma. Through the networkanalysis of Oryeongsan, alisol B 23-acetate, cinnamaldehyde, andbeta-eudesmol had many nodes in that order. Similarly in thetarget protein, CASP3, AT4G13230, and MAOA had many nodes inthat order. On pathway analysis of protein targets associated withhypertension, the metabolic pathway was the most relevant andrenin-angiotensin pathway was also relevant.In conclusion, Oryeongsan is associated with phlegm-retainedfluid related diseases. And the mechanism of action forhypertension seems to be related to pathway of renin-angiotensinsystem, renin secretion and endocrine and other factor-regulatedcalcium reabsorption.