Syndrome differentiation of defensive qi, qi, nutrient qi and blood is a syndrome differentiation method for exogenous epidemic febrile disease developed by Ye Tianshi in the Qing Dynasty. It summarizes the symptoms of exogenous epidemic febrile disease at different stages into four types for the benefit of treatment, namely defensive phase syndrome, qi phase syndrome, nutrient phase syndrome and blood phase syndrome.
 
Syndrome differentiation of defensive qi, qi, nutrient qi and blood was developed on the basis of six-meridians syndrome differentiation due to cold attack, replenishing six-meridians syndrome differentiation and enriching the content of syndrome differentiation for exogenous febrile disease.