Abstract: In order to determine the optimum protein supplementation and the optimum supplementation time before breeding for production of quality semen of rams of Chinese Merino（Xinjiang Junken type） fine hair sheep, twelve 3-years-old rams with physical soundness and standard breed performance records were randomly divided into 4 groups, among which, the control group was fed an essential diet with a protein level of 12%, the other 3 experimental groups were groups with a low, medium and high protein supplementation which were fed protein level of 14%, 16%, and 18% by adding soybean meal to the diets, respectively, for a pre-feeding period of 30 d and an experimental period of 56 d. During the period of experimentation, after rams were fed in the morning, semen was collected by using the sham vaginal method on every mor-ning for an immediate evaluation of ejaculate volume, semen density, sperm viability and sperm vitality. The results showed that supplementation of soybean meal with different protein levels in the diets significantly affected ejaculate volume and semen density of Chinese Merino fine hair rams（P ＜ 0.05）, but there was no significant difference between other traits for different supplementation levels（P ＞ 0.05）; sperm viability at 42 d and sperm motility at 42 d and 49 d in the low protein level group were significantly different from the other 3 groups（P ＜ 0.05）. It can be deduced that the pre-breeding nutritional needs of the rams of Chinese Merino（Xinjiang Junken type） fine hair sheep could be met by a 14% protein supplementation in the diets, and the optimum semen quality of the rams could be achieved at days of 72 to 79 during the supplementation period（30 d pre-feeding period + 42-49 d experimental period）.