The milk clotting properties of bovine pepsin extracted from stomach mucosa of Korean cattle was investigated as a milk clotting enzyme for rennet substitutes. The results obtained were summarized as follows; 1. The weight of raw abomasum was 1,203g per head and separated mucosa was 520g and the amount of extracted pepsin solution was 1,214 ㎖ and about 100 ℓ milk was coagulated by the pepsin solution per head. 2. The milk clotting activity of bovine pepsin was extremely pH-dependent around pH 6.8 and above pH 7.0, the activity falled. 3. The optimum coagulating temperature appeared between 40∼47℃ and above 57℃ the activity fell and the activity was decreased below 30℃. 4. Pepsin coagulating time was seemed to decrease with increasing sodium chloride concentration in milk and to increase with calcium chloride concentration. 6. The milk clotting activity of bovine pepsin was not significantly affected by antiseptics after storage at 35℃ for 12 hours. 6. The rate of curd yield by bovine pepsin for cheddar cheese making was 10.25% to the amount of clotted milk and it was similar to that of calf-rennet.