Raw materials were the potato starch residue generated in the production process. The potato starch residue was made into the materials for fermentation by adding rice bran to reduce moisture content to 72%, and then adding superphosphate calcium and lactobacillus. The fermentation materials adding different amount of urea were set to anaerobic fermentation. By the determination of crude protein, true protein, urea residue, acidity, lactic acid content and other indicators of fermentation products, it was found that adding urea had a significant influence on the residue quality of potato starch＇ s anaerobic fermentation, and the best quality was got by adding 2.0% -2.5% of the amount of urea.