Doctor Mao Dexi learnt the essence from different schools of Chinese medicine，especially the study of classical TCM formulation.He used classical TCM formulation theory to guide clinical practice，treated miscellaneous and difficult diseases with classical TCM formula.Special emphasis was paid to distinguishing main syndromes，selecting main formula and main drugs，which is the best example of convenience，simplicity，low price and good efficacy.Doctor Maos Sanwei formula was derived from the classical formula，with some variations，it saved lives of many.The paper summarized and explained usage of Sanwei formular for reference.