This paper studies the medical thought of Chang-Tsu Li who was one of most famous doctors who were skilled in tonic and nourishing treatment at the end of Ming dynasty. From studying his book ”Yi-Zone-Bi-Dou” and ”Shan-Bu-Yi-Sheng-Wei-Lun”, he said that they were important in treatment of diseases to find out the etiology, to verify the pathology of viscera and to balance the regulation of Qi. Dr. Li was also one of the great figures in the ”Yi-Shuei” (易水) school since he strongly believed in that the tonic of the ”chi” and the nourishing of the ”yang” must be firstly and equally applied to patients for their ”kidney” and ”spleen” for asthenic and chronic diseases. For similar syndromes, he referred pulse and symptom to differential diagnosis. Dr. Li learned from Masters ”Li-Zhai Xue (薛立齋) ” and ”Jie-Bin Zhang (張介賓)” who paid much attention to congenital essence. However, the ”Radix Rehmanniae” (地黃) was not the only tonic drug used by Dr. Li to improve the ”kidney”. Dr. Li also followed Masters ”Yuan-Su Yuan” (張元素) and ”Dong-Yuan Li” (李東垣) to lay stress on acquired essence. But, Dr. Li believed that Rhizoma Cimicifugae (升麻) and Radix Bupleuri (柴胡) were not the only way to nourish the ”spleen”. In conclusion, Dr. Li collected all the Masters' knowledge but abandoned their deficiencies. No wonder he plays a very important role in Chinese medical history.