Abstract:There are many factors affecting the quality of pasteurized milk，among which the quality of raw milk is one of the important factors affecting the quality of pasteurized milk. In this study，high -performance liquid chromatography and a milk composition analyzer were used to analyze the nutritional composition，microbial conditions，and changes in active substances of raw milk produced by dairy farms in different seasons，and the results were used this as a reference for screening raw milk sources for pasteurized milk. The results showed that the indexes of raw milk from different sources showed regular fluctuations with seasonal changesvariations.The fat and protein contents of most raw milks were the highest in winter and the lowest in summer，but the total number of colonies and the number of somatic cells showed the opposite trend. The content of αlactalbumin，β-lactoglobulin，and lactoferrin，and other active substances showed the same trend of as that ofthe contents of active substances as the basic ingredients.Different feeding and，management practices，and geographical factors also affected the quality of raw milk，and the fluctuation of nutrient content with seasonal changes variations was smallslight.