The project was planned to produce max. protease from Whey by Rhizopus arrhizus at pH 4 and 37C temperature. Growth media employed to culture R. arrhizus for the production of enzyme were developed and fermentation conditions was optimized through various trials. Substrate water ratio, different nitrogen sources and cont. of nitrogen source were optimized. The fermented materials were harvested after 72 hours. These were filtered and centrifuged at 10,000 rpm at -10C. The filtrates were subjected to enzyme assay. Absorbance of the enzyme sample was determined at 660 nm on spectrophotometer. The enzyme activity was calculated and the results were analyzed statistically by using ANOVA under CRD and by taking MSE from ANOVA, DMR test w sap-lied to compare the treatment means. It was observed that 90% Whey and 2.5% cotton seed meal enhanced the production of protease by R. arrhizus. Max. enzyme activity was observed (149.26 IU/ml/min) in flask level at pH 4 and 37C temperature. These optimized conditions of growth media was again used in Air-Lift fermenter and determined the activity (169.78 IU/ml/min) that is greater than flask level. This is due to temperature in Air-lift fermenter.