Radiation-induced lung injury （RILI） is caused by the "heat toxin" of radiation. Based on the clinical manifestation and the pathological characteristics of RILI in different phases in modern medicine， RILI is divided into three phases， that is intense heat toxin phase， yin deficiency and heat accumulation phase， and static blood obstruction phase， for which "three phases and three methods" has been proposed to prevent and treat RILI. For the early stage of RILI， that is intense heat toxin phase， it is recommended to use the method of clearing the lung and resolving toxins， usually with Yin Qiao Powder （银翘散） in modifications. Regarding the middle stage which is yin deficiency and heat accumulation phase， the method of enriching yin and venting heat is recommended， often using self-made Yangyin Qingfei Formula （养阴清肺方）. In terms of the late stage， that is the static blood obstruction phase， It is recommended to invigorate blood and dissolve stasis， usually with self-made Qingfei Huoxue Formula （清肺活血方）.

Radiation-induced lung injury is a prevalent side effect of radiotherapy for chest cancer. The "three phases and three methods "is an innovative theory based on the evolution of the core pathogenesis of radiation-induced lung injury. Its formation also considers the understanding of radiation-induced lung injury by ancient and modern medical practitioners, pathological characteristics, clinical manifestations, and the development patterns of radiation-induced lung injury. The "three phases and three methods" refers to the three phases of the course and the three treatment methods. The core pathogenesis of radiation-induced lung injury from the beginning, middle and late stages is heat toxicity, yin deficiency, and blood stasis. Therefore, the course of radiation-induced lung injury is divided into three phases: blazing heat toxin, yin deficiency and heat accumulation, and static blood obstruction. The method of clearing the lung and resolving toxins, enriching yin and venting heat, invigorating blood and dissolving stasis are used respectively. Traditional Chinese medicines commonly used in each phase include Flos Lonicerae, Atrina Glass, heartleaf houttuynia herb, Radix Ophiopogonis, American Ginseng, Forsythiae Fructus, Radix Salviae Miltiorrhizae, Rhizoma Ligustici chuanxiong, Scorpio, etc. This article presents the theoretical origins of the "three phases and three methods" concept by reviewing of ancient literature, inheriting experience, and summarizing disease pathogenesis, as well as elaborating on the academic connotations of the "three phases and three methods". The scientific validity of the "three phases and three methods" is verified by literature, clinical, and basic research. The "three phases and three methods" interprets the core characteristics of each stage of radiation-induced lung injury, improves the traditional Chinese medicine prevention and treatment system for radiation-induced lung injury, and provides theoretical basis for achieving complete process management.