To observe and analyze syndrome law of multiple system atrophy (MSA). Methods:It was a cross-sectional study. General information and four diagnosis information of MAS patients meeting western medicine criteria were collected. And specific syndrome of each case was differentiated, to extract syndrome elements. Frequency of syndrome elements and percentage were calculated. Distribution of syndrome elements was concluded. Type and mean value were used to compare the group of syndrome elements. And the correlation between syndromes and course of the disease, syndromes and severity, syndromes and type of the disease of all MSA patients were evaluated. Results:The mechanism of MSA was more deficiency and less excess. There were more heat and blood deficiency in MSA-P type, with more cold and qi deficiency in MSA-C+P. Qi deficiency was commonly seen in C+P type, and blood deficiency was frequently seen in P type. Qi deficiency was often together with cold syndrome, and often seen in the middle and advanced stage of disease. Heat syndrome was often together with blood deficiency, and often seen in the early stage of disease. Kidney deficiency was often seen in C+P type, and liver disease, heart disease were often seen in P type. Spleen deficiency and stomach disease were often seen in C type. Phlegm and damp were more frequently seen in P and C+P type. Blood stasis was more frequently in C+P type, and qi collapse only in C+P type. Deficiency and excess were both increased with the progress of MSA. Conclusion:Key mechanism of MSA was Yang deficiency of kidney. TCM treatment principle of MSA was warming kidney and supporting Yang.