Abstract: Cassava liquefied supernatant was used as sugar, and corn syrup and soybean meal were added as nitrogen for citric acid fermentation according to the proportion of 3：1 to prepare the fermentation medium with total protein content of 0.6% （m/m）. Under the conditions, the fermentation cycle was 60 h; the ratio of citric acid was 16.8% （m/v）; the total sugar residues was 0.8% （m/v）; and the ratio of transforming was 98.8%.