Abstract: Four common agricultural products,namely potato,yam,taro and Jerusalem artichoke were chosen for the experiment.They were dealt with water,enzyme and water－ enzyme combined respectively.Then the treated liquid was added to the soybean milk to be mixed well.Sterilization,cooling,inoculation and fermentation were followed.It showed that the filtered liquid of Jerusalem artichoke was the best to promote the growth of the bifidobacterium,and the optimum,concentration was 0.1％～ 1％ and the fermentation cycle was 4 hours or so,shorter than the control.The number of live bacteria could reach 109CFU/ml the product.