Abstract: Under grazing condition, some Bayinbuluk sheep and its crossbred with Dorset were selected as subject, observe their growth from birth to six months old. In addition, observe effect of supplement of pregnant ewe on their lambs. Results showed that maximum growth is from 2 to 3 months, then from 1 to 2 months， 0 to 1 months. The body weight decreased from 4 to 5 months.Then increased from 5 to 6 months. Supplement to pregnant ewe has not effect on their lambs. Significant advantage on growth of crossbred of Dorset and Bayinbuluk sheep can be observed.

Key words: body weight gain; growth rule; Bayinbuluk sheep