Yinqiao San is the medicine for the outer part disease of the human body. In ${ulcorner}$Wenbingtiobian${lrcorner}$, this medicine is the most useful when it is used within short time after the starting boiling it. In this study, the volatile ingredients of the Yinqiao San were observed by GC and compared with each other in time scale. Most of the ingredients were observed about 5 min after the starting boiling it, after10 min., the GC peaks were smaller and smaller, and after 2 hours and 30 min. the GC peaks were almost gone. It is confirmed that was written about the Yinqiao San in ${ulcorner}$Wenbingtiobian${lrcorner}$.