This experiment was conducted in order to describe the effective method, the morphology and mechanism of the meiosis of chromosome during the spermatogenesis in Bulls. The results obtained can be summarized as follows: 1. The most effective incubation temperature and optical length of culture have turned out to be 31℃ and to 2h.. A maximum cell division has reached at 24∼72 hours after beginning of culture. 2. Cultures with serum in minimum essential medium(MEM) and Basal medium eagle(BME) showed distinct stimulation. A striking smaller cell division was observed in the cultures with serum addition in medium 199. Maximal stimulation to cell-division has been achieved with a 10% addition of fetal calf serum. The cell-density from 8,000 cells/㎣(=8 x 10^6ml) in medium was found as ideal. 3. Morphology of Meiosis chromosome, mechanism, differentiation of sex-vesicle and sex chromosome were observed.