Soybean and skim milk were used as the raw material to produce soymilk yoghurt by mixed fermentation of L4-4( Lactobacillus casei) and L6-2( L. fermentum). The suitable conditions were determined by single factor experiment as follows: the ratio of L4-4 and L6-2 was 1∶ 1,inoculation amount 5%,ferment at 37 ℃ for 12h. The sensory index and nutrition constituent was compared between mixed fermentation and single-strain fermentation. The results showed that the sensory index of mixed fermented soymilk yoghurt was better than that of L4-4,while the effect of refining nutrient by mixed fermented was superior to that of L6-2.