Abstract: In order to explore the relationship between body weight and body size and tail traits indexes in Sunit sheep, 239 Sunit ewes（seventy nine aged 3 months, eighty aged 6 and 12 months respectively） were used as the study subjects.The body weight（Y）, body size（body height X₁, back height X₂, body oblique lengthX₃, chest width X₄, chest depth X₅, chest circumference X₆）, and tail traits(tail lengthX₇, tail width X₈, tail areaX₉, tail thicknessX₁₀, tail volumeX₁₁) indexes were measured/calculated. Correlation analysis, path analysis and stepwise regression analysis, between body weight and body size with tail traits indexes were performed by SPSS 23.0 software. The results showed that the higher coefficient of variation in Sunit ewes at different months were tail thickness, chest width and back height. Body size and tail traits in Sunit sheep at different months of age were significantly positively correlated with body weight（P＜0.01）. The correlation coefficients between body weight and body size with tail traits indexes in 3-month-old, 6-month-old and 12-month-old Sunit ewes from large to small in turn were chest depth＞chest circumference＞chest width＞body height＞back height＞tail area＞tail width＞tail volume＞tail thickness＞body oblique length＞tail length, tail area＞back height＞chest width＞tail width＞chest circumference＞body oblique length＞chest depth＞tail volume＞body height＞tail length＞tail thickness, and tail volume=back height＞chest circumference＞tail area＞chest depth＞tail width＞chest width＞body oblique length＞tail thickness＞body height＞tail length, respectively. The direct effects of body size and tail traits indexes on body weight in 3-month-old, 6-month-old and 12-month-old Sunit ewes from large to small in turn were tail area＞tail thickness＞chest circumference＞body height＞back height＞body oblique length＞chest width＞chest depth＞tail width＞tail length＞tail volume, tail area＞back height＞chest depth＞tail thickness＞chest width＞body oblique length＞tail length＞body height＞tail width＞chest circumference＞tail volume, and tail area＞tail thickness＞back height＞chest depth＞chest circumference＞body oblique length＞chest width＞body height＞tail length＞tail volume＞tail width. The indirect effects of body size and tail traits on body weight in 3-month-old, 6-month-old and 12-month-old Sunit ewes from large to small in turn were tail volume＞tail length＞tail width＞chest depth＞chest width＞body height＞body oblique length＞back height＞chest circumference＞tail thickness＞tail area, tail volume＞chest circumference＞tail width＞body height＞tail length＞body oblique length＞chest width＞chest depth＞back height＞tail thickness＞tail area, and tail width＞tail volume＞tail length＞chest width＞body height＞body oblique length＞chest circumference＞chest depth＞back height＞tail thickness＞tail area. The body size and tail traits with high decision coefficients on body weight in 3-month-old, 6-month-old and 12-month-old Sunit ewes from large to small in turn were chest circumference＞body height＞back height＞chest width, back height＞chest width＞chest depth＞tail thickness, and back height＞tail thickness＞chest depth＞chest circumference respectively. The optimal regression models in 3-month-old, 6-month-old and 12-month-old Sunit ewes were Y=-5.248+0.077X₁+0.093X₂+0.087X₄+0.084X₆+0.440X₈+3.237X₁₀-0.009X₁₁（R~2=0.873,P=0.052）,Y=26.828-0.478X₁+0.980X₂+0.584X₄+0.682X₅-0.445X₆+0.169X₉+1.539X₁₀-0.009X₁₁（R~2=0.842,P＜0.05）,Y=11.061+0.842X₂-0.282X₄+2.146X₁₀+0.002X₁₁（R~2=0.949,P＜0.05）, respectively. The results indicated that the early breeding of Sunit ewes was mainly based on chest depth, chest width, and chest circumference, as well as back height, tail width and tail thickness. Tail thickness, which could reflect fat deposition condition in the production, had the largest coefficient in the regression equations above, which should be considered comprehensively in breeding.