Abstract: Winter feeding is a very important practice in sheep farming in Inner Mongolia grassland pastoral areas. The aim of this study was to determine the effects of supplementary feeding before lambing on sheep weight and body size, and economic benefits. Sixty pairs of Hulun Buir short-tailed sheep were selected as the test subjects. One month before lambing, the experimental group was fed with concentrated feed, and the control group was fed with only hay. Changes in the body weight, body size, and economic benefits of livestock within 100 days were analyzed. Variance analyses were conducted with SAS (statistics analysis system) and partial least squares regressions were conducted with SIMCA-P11 (simple principal component analysis). These analyses allowed us to determine the effects of prenatal feeding on the individual and production efficiency of livestock, and on the main body weight of livestock. The results showed that, in the 100-day period, the weight of females decreased and then increased. The chest circumference, chest width, body height, chest depth, body length, and body oblique length were significantly higher in the experimental group than in the control group at about 1 month after birth (P<0.05). The main indexes influencing the body weight of Hulun Buir short-tail sheep were chest width, body height, and chest depth; together, these factors explained more than 50% of the variance in body weight. The survival rate and the selling price of newborn lambs was significantly higher in the experimental group than in the control group (P<0.05). Supplementary feeding before lambing not only affected the body weight and body size indexes, but also played an important role in improving the survival rate and increasing economic benefits. These results provide a theoretical basis for the breeding and care of ewes and the precise elimination of livestock.