Professor LI Shimao′s experience of applying Guizhi Decoction（桂枝汤） in clinical practice is summarized. Guizhi Decoction′s connotation

indications and correlation on change and development of its modified formulas are interpreted from the angles of principle

method

recipe and medicines. It is believed that the application of Guizhi Decoction emphasizes on basic matching. It is not only a sweating formula

but also a supplementing one. It is called a light supplementing formula for yin and yang

and it can be derived into many formulas

which can be used for both endogenous and exogenous diseases in clinical practice. On the basis of "proceeding and ceasing method" of Guizhi Decoction

"three auxiliary methods for sweating"（taking medicine continuously

having porridge and covering up to keep warm） are summarized to help sweating and protecting vital qi.