Glucose is a common carbon source for the high cell density cultivation of E.coli.However, when the ratio of carbon and nitrogen isn't suitable to the cultivation progress, great amounts of organic acids would be produced and would inhibit the growth of bacterial and synthesis of human-like collagen.In order to reduce the production of by-products, especially organic acids, the ratio of carbon and nitrogen in the medium for E.coli BL213.7 was optimized.