[Objective] To explore the relationship between brittle diabetes and yin fire, so as to more comprehensively understand fragile diabetes from TCM, broaden the clinical diagnosis and treatment, and improve the clinical curative effect. [Methods] The theory of yin-fire theory was summarized, and the relationship between brittle diabetes and yin-fire was expounded from the aspects of academic origin, pathological basis, clinical manifestation and so on, proposed treatment principles and prescriptions.[Result] The yin fire theory originated from Nei Jing. Yin and yang do not rise, wet muddy bets, endogenous fire, the fire is too weak. Fever is the reason for the formation of diabetes, Yin fire is an important reason for fluctuations in blood sugar; brittle diabetes expelling Bu Zhong Yi Qi, lifting fine, Xie Yin fire, from Dongyuan Qingshu Yiqi Decoction to the treatment of fragile diabetes sugar made a good effect. [Conclusion] The theory of yin fire has important practical significance for diabetes, especially brittle diabetes. It is a new idea and method to treat brittle diabetes by the thought and method.