Cellulose is most abundant biological component on terrestrial and aquatic ecosystem. Being the largest component of terrestrial and aquatic ecosystem conversion of this complex carbohydrate to a simpler sugar is having brighter future. The conversion of cellulose to one of the simplest form of sugar which is glucose is having bright future. Some and bacteria are capable of these conversion so in this experiment our main objective was to produce high yield of cellulase using Bacillus flexus strain. Various multiple factors was tested for cellulase productivity by Bacillus flexus strain using Taguchi methodology based on Design of experiments and dinitro salicylic acid (DNSA) technique was used for quantifying the cellulase productivity. The optimum pH and temperature for enzyme activity was 6 and 25 respectively and most prominent nitrogen source was peptone and whereas optimum cellulose and tween80 concentration was found to be 2% and 1% respectively. It shows that pH should be low, nitrogen should be high, cellulose should be low, tween80 should be low and temperature should be moderate. ANNOVA shows nitrogen has highest percentage contribution (38.07%) then pH has 24.784% contribution followed by tween80 which has 16.087% contribution then cellulose has 15.441% contribution and temperature has lowest % contribution (5.616). Maximum enzyme activity was found in trial condition 4 and is 0.25192 IU/ml.