Abstract: BLUP method with animal model was used to estimate heritability of body size traits of fat-tail sheep.The results showed that the heritability of body weight,body height,body length and chest circumference was 0.14,0.11,0.11 and 0.15,all of which were moderate heritability（0.1h20.3）.The heritability of tail length and tail width was 0.09 and 0.08,both of which were low heritability（h20.1）.We proposed the BLUP method and marker-assisted selection（MAS） be used to select fat-tail sheep so as to increase the accuracy of breeder selection.