The invention provides a process of preparing fermented milk beverage keeping high viable cell count at ambient temperature. The process includes the steps of adding regular yoghurt lactobacillus into milk for fermentation, fermenting until pH value to 3.8-4.8, diluting, mixing and sterilizing with conventional method, adding concentrated culture, concentrated frozen culture or freeze dried culture containing Lactobacillus rhamnosus ATCC 53103 into mixed milk beverage at aseptic condition. According to various pH value of finished product, it can be stored at ambient temperature for 1-6 months, and the viable cell count will not be less than 105 cfu/ml milk beverage. The indexes of storage period and viable cell count are much higher than fermented milk beverage produced by conventional process. Thereby the defect that fermented milk beverage has short shelf life and low viable cell count at ambient temperature is overcome efficiently.
