To understand the genetic parameters for early body weight of hens, we used White leghorn reciprocal crossing with the blue eggshell hens to generate F2 population and then performed genetic analysis. The results showed genes on Z chromosome contributed to the genetic additive variances of early body weight. The fix effects included breed, generation and inbreeding coefficients. The heritability on body weight at the age of 3 week in F2 population was 0.52±0.03, and 0.07±0.02 contributed from Z chromosome. Our study indicated that genetic evaluation on the early body weight should include the sex linkage effect. The heritability estimates were moderate to high for the body weight at the third week. For further study, it is better to select individual culture.