Abstract: [Objective] To explore the correlation between body weight and body size indexes of Sadumun ternary crossbred black sheep, and to construct an optimal regression model of body weight-body size indexes for black sheep. [Methods] Sixty 8-month-old Sadumun ternary crossbred black sheep rams were selected for the study, and their chest circumference, body height, body length, body slant length and body weight were determined. The statistical software of SPSS 26.0 was used to carry out correlation analysis, regression analysis and path analysis of the collected data, and then to establish the regression equations. [Results] There was a highly significant （P<0.01） positive correlation between body weight and body size indexes of Sadumun ternary crossbred black sheep, and the correlation coefficient between chest circumference and body weight was the largest, which was 0.755. Path analysis showed that chest circumference, body height and body slanting length were important variables affecting body weight, and had an indirect effect on body weight through body slanting length. The optimal regression equation of body weight and body size index of Sadumun ternary crossbred black sheep was y=0.971x_{chest circumference}+0.629x_{body height}+0.505x_{body slant length}-127.019, and the standardized regression equation was y=0.644x_{chest circumference}+0.333x_{body height}+0.335x_{body slope length} （R²=0.761, P<0.01）. [Conclusion] There was a highly significant （P<0.01） positive correlation between body weight and body size indexes of Sadumun ternary crossbred black sheep. The chest circumference, body height and body slant length had a direct impact on body weight. In the process of breeding, the body weight of sheep could be effectively predicted and increased by optimizing these indexes.

Key words: Sadumun ternary crossbred black sheep, body weight, body size, correlation analysis, regression analysis