This experiment was carried out to develop an ideal diluter for the preservation of boar semen. Ten excellent diluters previously reported by other workers in and out of the country were selected for the test. Diluted semen at the ratio of 1 to 3 were preserved at 0-5℃ and 15℃ respectively. During the preservation-period, sperm motility and livability were examined 6 times every 24 hours for 120 hours. The results were as follow: 1. The excellent diluter was composed of glucose … 1.5g fructose … 1.5g tris. … 3.028g citric acid … 1.74g glycine … 0.047g catalase … 0.02㎖ egg yolk … 20% distilled water … 100㎖ 2. Sperm motility of this diluter for 0, 1, 2, 3 and 4 days were 72%, 63%, 58%, 53%, 17% and 0%, respectively. 3. Preservative temperature at 15℃ was better than 0-5℃.