Written by Zhang Song, a physician in the Southern Song Dynasty, Jiu yuan fang (Formulary of Exploring Cause) was a lost clinical experienced formulary book. Totally 124 items of its original texts were quoted and remained in some other ancient Chinese medical books, such as Fu zai wan an fang (Formulary for Absolute Safety), Bao qing ben cao zhe zhong (Compromised Materia Medica of Baoqing Reign), Bencaogangmu (Compendium of Materia Medica) and Puji Fang (Prescriptions for Universal Relief) etc. After compiling and editing these scattered records, it was found that Jiu yuan fang was the earliest book carrying the Yupingfeng Powder, with rather high value of literature research and significance of clinical application.
《究原方》是南宋医家张松撰写的一部临证集验方书，已佚。《覆载万安方》《宝庆本草折衷》《本草纲目》《普济方》等古籍文献中，引有124条该书原文。通过辑佚发现，《究原方》是目前发现最早记载玉屏风散的书籍，具有较高的文献价值和临床应用价值。.
Keywords: Jiu yuan fang (Formulary of Exploring Cause); Yupingfeng Powder; Zhang Song.