In present studies, some data on the Mucor miehei rennet milk clotting time at different pH and temperature has been studied. Milk clotting time of Mucor miehei rennet from 30 to 70 degrees C of temperature in pH range of 5, 6, and 7 were obtained. Effects of temperature, pH and the interaction of temperature and pH on milk clotting time of Mucor miehei rennet were changed significantly. Effects of temperature and pH were investigated with 2 factors factorial design. Multiple comparsions of parameters were made by the homogenous Subsets. The homogenous of the temperature and pH were determined through post hoc test. Statistical evaluation of the results showed that the assay results are in good agreement.