Abstract: In order to study the correlation between body weight and body size in Duolang sheep and the second generation of the cross between Duolang sheep and Hu sheep（Duohu F2 generation）, SPSS 25.0 software was used to perform t-test on a total of 97 Duohu F2 and 101 Duolang sheep, the body weight of the two populations at different months of age（0, 3, 6, 12 months old）. At the same time, phenotypic analysis, correlation analysis, regression analysis were performed on the 3-month-old body weight and body size of the two groups, and the optimal regression equation was established. The results showed that the body weight of Duohu F2 generation at different months was higher than that of Duolang sheep, and the 3-month-old body weight was significantly higher than that of Duolang sheep（P＜0.01）. The coefficient of variation of body weight of 3-month-old Duohu F2 generation and Duolang sheep was the largest, which were 14.09% and 14.29% respectively. Among the body measurements, except for the chest circumference and cross height, other body size indicators of the 3-month-old Duohu F2 generation lambs were lower than Duolang sheep; chest size has biggest effect on weight in all body size indicators, the correlation coefficients were 0.727 and 0.625 respectively. The 3-month-old weight（y） in the two groups was extremely significantly positively correlated with body height（x₁）, body length（x₂）, chest circumference（x₃）, chest depth（x₄）, chest width（x₅）, tube circumference（x₆）, and cross height（x₉, P＜0.01）, and was significantly positively correlated with ear length（x₇） and ear width（x₈, P＜0.05）. Among them, the chest circumference of Duohu F2 generation lambs was extremely significantly positively correlated with chest depth, chest width, tube circumference and cross height（P＜0.01）, and was significantly positively correlated with ear width（P＜0.05）. The chest circumference of 3-month-old Duolang sheep was significantly positively correlated with chest depth, chest width, and tube circumference（P＜0.01）, and was significantly positively correlated with cross height（P＜0.05）. The body height, chest circumference, chest depth, and chest width of 3-month-old Duohu F2 generation lambs had a extremely significant effect on the weight（P＜0.01）, and the optimal regression equation was y_{（Duohu F2 generation）}= 0.254x₁+ 0.397x₃+ 0.366x₄+ 0.418x₅-36.505. The body height, chest circumference, and chest depth of 3-month-old Duolang sheep had a extremely significant effect on the weight（P＜0.01）, and the optimal regression equation was y_{（Duolang sheep）}= 0.243x₁+ 0.399x₃ + 0.256x₄-24.920. The results indicated that body height, chest circumference, chest depth and chest width could be used as important body size indicators for breeding of 3-month-old lambs of Duohu F2 generation. Body height, chest circumference and chest depth could be used as important body size indicators for breeding of 3-month-old lambs of Duolang sheep.