OBJECTIVE: To analyze the effect of Chinese herbs used by Prof. LI Tao on peripheral blood T subsets in treating multiple sclerosis (MS) by using association rules and statistical methods, thereby providing evidence for optimizing prescriptions. METHODS: Data of MS inpatients and outpatients recorded by data collecting system, Xiyuan Hospital, China Academy of Chinese Medical Sciences were resorted. The relationship between Chinese herbs and T cell subsets were analyzed using SPSS17.0 and Aprior module in SPSS Clementine 12.0. RESULTS: Radix bupleuri, Radix Paeoniae alba, Fructus Aurantii, Atractylodes, and Radix Glycyrrhizae were most commonly used herbal combinations.Radix Aconiti lateralis preparata and Rhizoma Smilacis glabrae were often added. Radix Aconiti lateralis preparata was associated with decreased Th1 cells (confidence level 83.78%, supportive level 36.26%). Decreased Th1 cell was associated with Radix Aconiti lateralis preparata (confidence level 71.26%, supportive level 36.26%).Radix Aconiti lateralis preparata was obviously associated with decreased Th1 cells. Radix Bupleuri, Radix Paeoniae alba, bitter orange, Atractylodes , Radix glycyrrhizae, and Radix Aconiti lateralis preparata could reduce peripheral blood Th1 subsets of MS patients and elevate Th2 subsets (all P < 0.01). CONCLUSIONS: The herbal combination of Radix Bupleuri, Radix Paeoniae alba, Fructus Aurantii, Atractylodes, Radix Glycyrrhizae, Rhizoma Smilacis glabrae, and Radix Aconiti lateralis preparata could lower peripheral blood Th1 cells and elevate Th2 cells, and prevent the relapse of MS possibly by reducing Th1 cells and elevating Th2 cells. Especially Radix Aconiti lateralis preparata played important roles in aforesaid changes of Th1 and Th2.