Yoghurt starter can be divided into three types according to different physical forms: liquid yogurt starter, frozen yogurt starter and direct-injection yogurt starter. Liquid yogurt starter is relatively cheap, but the viability of the strains often changes, and it is easy to be contaminated by miscellaneous bacteria during storage. The storage time is also short, and the viability of the strains decreases quickly during long-distance transportation. Frozen yogurt starter is made by deep freezing. Its price is also cheaper than direct-injection yogurt starter, with higher bacterial viability and shorter activation time, but it requires special environmental conditions of about -45~-55℃ during transportation and storage; while direct-injection yogurt The starter culture can not only be directly put into the fermentation tank to produce yogurt, but can also be stored in an ordinary refrigerator. The transportation and storage costs are very low. Its convenience, low cost and quality stability during use are particularly outstanding.