Abstract：Objective：To sort out and summarize QIAN Yi's understanding of malnutrition syndrome， to analyze the formulas of QIAN Yi treating malnutrition syndrome in children and summarize the administration rules and his academic thoughts. Methods：After reading the book Xiao Er Yao Zheng Zhi Jue (Qian's key to Diagnosis and treatment of Children's Diseases)， the understanding of malnutrition syndrome by QIAN Yi was sorted out and summarized， and elaborated from the aspects of etiology， pathogenesis， classification， clinical manifestation， and syndrome differentiation and treatment. The formulas for malnutrition in children were screened，and such data as the frequency of Chinese herbs used in formulas as well as their four qi，five flavor and channel entry were statistically analyzed by the Ancient and Modern Medical Cases Cloud Platform (ckcest.com). Results：QIAN Yi believed that there were four main causes of malnutrition syndrome， namely misdiagnosis， long- lasting diarrhea and vomiting， improper diet， and long- lasting malnutrition with food accumulation; the main pathogenesis included spleen- stomach weakness and body fluids consumption. QIAN Yi classified the malnutrition syndrome into the heart malnutrition， the liver malnutrition， the spleen malnutrition， the lung malnutrition， and the kidney malnutrition; in addition to the above five types， there were also internal malnutrition， external malnutrition， sinew malnutrition， bone malnutrition， fright malnutrition， and scabies; the symptoms of each type were described. QIAN Yi considered that， in the syndrome differentiation and treatment of malnutrition syndrome， the “mother” viscera should be tonified according to the motherchild relation among the five viscera， the selection of formulas should be based on the situation of the patients， whether there is cold or heat and whether the patient is fat or thin， and the medication should be based on the course of the disease. In 34 formulas for malnutrition syndrome ， a total of 93 Chinese herbs were involved. The mostly used herbs were Coptidis Rhizoma， Moschus， Crotonis Fructus， Aucklandiae Radix， Calomelas， Picrorhizae Rhizoma， Indigo Naturalis， Cinnabaris， Bufo Gargarizans and Borneolum Syntheticum and Glycyrrhizae Radix et Rhizoma，among which the core herbs were Coptidis Rhizoma，Picrorhizae Rhizoma and Moschus. In terms of analysis on the five flavor，pungent herbs were used for 74 times with a proportion of 38.14% ； bitter herbs were used for 68 times with a proportion of 35.05% ； sweet herbs were used for 38 times with a proportion of 19.59%. The four qi of adopted Chinese herbs were mostly cold and warm in nature. Among them， the herbs with cold nature were used for 57 times with a proportion of 29.38%；the herbs with warm nature were used for 46 times with a proportion of 23.71%；the herbs with balanced nature were used for 20 times with a proportion of 10.31%. The channels entries of more than a half of above herbs with warm nature were the spleen channels and the stomach channels，accounting for 32.47% and 28.35% respectively，and those of the rest were the colon channels and the liver channels， each accounting for 22.16% . Conclusion： The characteristics of administration rules of QIAN treating malnutrition syndrome in children are to relieve heat to benefit the spleen by bitter herbs，move qi and enliven the spleen by pungent herbs，and to benefit yin and tonify the spleen by sweet herbs； cold herbs were mainly adopted in treatment， supplemented by warm and balanced herbs； great attention was paid to the spleen and stomach； the treatment for five viscera based on syndrome differentiation was created for pediatrics，and Wuzang Buxie Prescription was prepared for the diagnosis and treatment of malnutrition syndrome；QIAN does well in using metallic and toxic herbs；the thought of preventing diseases was highlighted，that is，“Preventing diseases before it arises，and controlling the development of existing diseases ”.