ZHANG Xichun was a renowned medical practitioner of the confluence of Chinese and western medicine group and was the author of Records of Chinese Medicine with Reference to Western Medicine.He expanded and changed the theories of Chinese medicine，and his theory of Daqi is one of the most innovative theories.Daqi is a subtle substance that accumulates in the chest with vital energy as the base and grain and clear qi as nutrients.Its main functions are to regulate respiration，move blood and qi，enrich nutrient defense，unify the triple energizer，and mediate the brain.The pathological changes are no more than the upward rebellion of Daqi，the deficiency of Daqi，and the stagnation of Daqi.“Headache is believed to be a disease of cranial nerves in western medicine”，and its pathogenesis is related to Daqi in the chest.It is believed that the pathological basis of headache is the loss of function of Daqi and the disorder of the brain.The upward rebellion of Daqi，the deficiency of Daqi，and the stagnation of Daqi are important pathogenesis.The treatments are to calm and subdue the upward rebellion，to raise and tonify the deficiency，and promote and relieve the stagnation，thereby tonifying Daqi and regulating the qi and blood to harmonize the brain.