Abstract：ZHOU Zhongying，a Chinese medicine master，put forward the theory of latent poison for difficult-to-treat diseases，which is characterized by the fact that the poison is unconscious and only appears when it occurs，and he pointed out that the deficiency of healthy qi is the foundation of latent poison. Multiple sclerosis is an autoimmune disease of the central nervous system，which has a long course and is easy to relapse，and there is no specific and effective treatment. It is consistent with latent poison in etiology and pathology. The authors discussed the etiology， pathogenesis， diagnosis and treatment of multiple sclerosis in Chinese medicine based on the theory of latent poison，and proposed that the pathogenesis of multiple sclerosis is the internal production of latent poison and marrow injury by latent poison caused by kidney deficiency， and that its treatment should be tonifying the kidney as well as detoxifying.