A renowned literary figure, politician, and medical scholar of the Tang Dynasty. Born in the seventh year of the Dali era (772) and passed away in the second year of the Huichang era (842), his ancestral home was in Pengcheng (present-day Xuzhou, Jiangsu). He was known as Liu Bin Ke because he once served as the Prince's Guest.

Yu Xi was frail and often ill from a young age, frequently seeking medical treatment and taking medicine. He had a considerable interest in medical studies. Persisting for thirty years, he eventually became a skilled physician. In treating diseases and prescribing medicine, he emphasized practical effectiveness, not rigidly adhering to ancient methods, and proposed the preventive idea of "preventing illness before it occurs, and treating it afterward." He was adept at using simple and proven prescriptions in treating diseases and valued the collection and organization of folk medical experiences. He was once commissioned to participate in the compilation of materia medica and classical formulas, and authored Chuanxin Fang in two volumes. This book includes ten prescriptions given to him by Xue Jinghui when he was in Lianzhou, along with over fifty effective folk prescriptions. Since each prescription was well-founded, it was named Chuanxin (transmitting trust). Its content covers various clinical fields, including emergency treatments, and is characterized by simplicity, convenience, and affordability in medication use.