Abstract: Using "Qula" as material, application effects of different chymosin in the process of casein production were researched. According to L₉(3⁴) orthogonal experiment, rennet, chymopapain and mucor pusillus chymosin were chosen for the production of chymosin casein. Considering economical effect, mucor pusillus chymosin was chosen as the suitable chymosin. The optimum technology parameters are as follows: concentration of mucor pusillus chymosin is 3.75 mL/g, pH value is 7, temperature is 55℃, and CaCl₂ addition is 12 g/kg. The percentage of manufacture obtained is 73.49%, sensory score is 9.49, protein content is 85.25%, ash component is 7.23% and fat content is 0.45%, meeting with the demand of QB/T3780-1999.