This article is based on the core pathogenesis of yin-yang poisoning recorded in the Synopsis of the Golden Chamber and clarifies the characteristics of"yin poisoning"and"yang poisoning"as considered during the Han and Tang dynasties.It is found that the classification criteria for the two are based on the manifestation of syndromes rather than the cold and heat of the pathogenesis.By analyzing the syndrome of yin-yang poisoning in the Synopsis of the Golden Chamber and combining the records with people's understanding of the efficacy of various medicinals in Shengma Biejia Decoction during the Han and Tang dynasties,it is demonstrated that the core pathogenesis is stagnation,mainly reflected in three aspects:accumulation of toxins,stagnation of qi and blood,and stagnation of yang qi.Among these,the degree and location of stagnation of yang qi are the reasons for the difference between yin poisoning and yang poisoning.The disease of yang poisoning is characterized by sufficient yang qi in the body,obstruction of pathogenic factors on the surface,and intense competition between vital qi and evil qi.Therefore,yang stagnation on the surface is more severe and leads to heat symptoms.The disease of yin poisoning is characterized by deficient yang qi in the body,an inability to resist pathogen,and the deepening of evil qi.The yang qi is suppressed by depression and is relatively mild,making it unable to circulate and warm the body,resulting in cold symptoms.Therefore,when treating yang poisoning,ZHANG Zhongjing used medicinals that were pungent,warm and dispersed to relieve the yang depression on the surface.If the yang depression was dispersed,the heat would naturally dissipate.When treating yin poisoning,only internal medicine is used to relieve internal yang qi stagnation,and when yang qi is extended,cold will naturally disappear.In summary,we aimed to enhance our understanding of the efficacy of Shengma Biejia Decoction from the perspectives of promoting the dispersion of toxins,promoting blood circulation,and promoting yang stagnation,in order to provide new ideas for the clinical use of this formula and expand its application scope.