Citric acid is a tri carboxylic organic acid is the most important acid produced by fermentation used in the food and pharmaceutical industries. The present work deals with determination of optimum growth conditions for citric acid production by submerged fermentation by using strain of A.niger MTCC662 respectively. Isolation, screening and mutated the A.niger strain induced by UV irradiation, diethylsulphate and Co60 by providing different types of media and the submerged fermentation was carried out under various growth parameters like temperature, pH and media of Sorghum malt as substrate. Strain improvement studies for maximum production of citric acid obtained after the fermentation. By using the response surface methodology has been optimized the production of citric acid. These variables were further optimized using a 24 full factorial CCD (Central Composite Design) and a second order polynomial model equation was obtained.