Abstract: In order to analyze the genes that played an important role in sex differentiation of birds, this study was designed to detect expression profiles of estrogens and its related genes in sex-reversed chicken embryos. In the present study, after injection with formestane and 17β-estradiol, expression of ER, 3βHSD, P450c17, and p450arom were measured at the early development stages (84 h, 96 h, 120 h, 144 h, 168 h and 192 h incubation) in chicken embryos by real-time PCR. Embryos treated with formestane and 17β-estradiol were designed as test group, while embryos non-treated but sex differential comprised control group. The results showed that: expression of ER, 3βHSD, P450c17 and P450arom in control group showed normal expression trend, but when compared with test group, the difference was significant (P＜0.05 or P＜0.01). For the test group, ER expression showed a downward trend, whereas, p450arom expression increased sharply. However, there was no obvious trend for the expression trend of 3βHSD and P450c17 genes. It was indicated that estrogen regulation was a complex process. Once injected with exogenous hormone, the normal regulation process would be disturbed significantly.