NOVELTY - Improving fermentation yield of L-arginine and conversion rate of saccharic acid, involves: fermenting L-arginine producing bacteria, where the initial or intermediate fermentation process is conducted in culture medium, and adding ferment auxiliary factor including: 0.01x 104 to 10x 104 g/l thiamine, 0.01x 104 to 2x 104 g/l riboflavin, 0.1x 104 to 10x 104 g/l of nicotinic acid and 0.01x 104 to 9x 104 g/l pyridoxamine, 0.01x 104 to 5x 104 g/l biotin, 0.05x 105 to 6x 105 g/l folic acid, and 0.01x 104 to 10x 104 g/l pantothenic acid.    USE - For improving fermentation yield of L-arginine and conversion rate of saccharic acid (claimed), where arginine is used regulating reproductive function and gene expression and in medicine and food industry.    ADVANTAGE - The method avoids use of extra equipment and reduce labor investment, shortens L-arginine fermentation production period and greatly improves yield and conversion rate, is simple and easy, and is suitable for industrial production. The L-arginine formed has wide application prospect in the field of nutrition control and adjusts internal secretion. The method avoids wastage of time and provides high yield of product, forms product of good stability and does not cause serious environment pollution and is suitable for large-scale production.    DETAILED DESCRIPTION - A method for improving fermentation yield of L-arginine and conversion rate of saccharic acid, involves: fermenting L-arginine producing bacteria to obtain L-arginine, where the initial or intermediate fermentation process is conducted in fermentation culture medium, and adding ferment auxiliary factor, where based on the total volume of the fermentation culture medium, the fermentation auxiliary factor includes: 0.01x 104 to 10x 104 g/l thiamine, 0.01x 104 to 2x 104 g/l riboflavin, 0.1x 104 to 10x 104 g/l of nicotinic acid and 0.01x 104 to 9x 104 g/l pyridoxamine, 0.01x 104 to 5x 104 g/l biotin, 0.05x 105 to 6x 105 g/l folic acid, and 0.01x 104 to 10x 104 g/l pantothenic acid.