Probiotics are ?"live microorganisms,which whenadministered in adequate amounts confer a health benefit on the host,?".Probiotic-yogurt has been accepted very well by consumers because of its unique characteristics,such as good flavor,nutritional value and health function,especially the physiological function by probiotics.However,because of the acid-producing ability and different metabolites,probiotics also affect the flavor of yogurt.Enough probiotics viable cells and the flavor changes of yogurt must be considered during the application.In order to compare the influence on flavor and acid of yogurt by different probiotics,LGG,NCFM,BB-12 and ABY were added into yogurt,the acidity,viable cells number of probiotics,and the content of diacetyl and acetaldehyde were analyzed when stored at 20℃.