Objective:To confirm if neuropeptide Y(NPY) is one of the most important factors in regulating GnRH release. Methods:In this study,we investigated the change of NPY expression in hypothalamus of common rats treated with the repeated EA at different developmental stages. Low frequency EA(3 Hz) was performed at acupoints(treatment groups) or non－acupoints (control groups) for 20 min daily for 10 days in Sprague－Dawley (SD) rats at four developmental stages,which were juvenile stage,early puberty stage,later puberty stage and adult stage. NPY expression in the hypothalamus was determined after 10－day treatment. Results:The results showed that NPY expression in the early pubertal group(EPG) was significantly depressed after repeated EA(P < 0.05). Compared with the results of GnRH expression and body weights,the change of NPY expression was similar with the fluctuation of GnRH expression after EA and the increase of body weights of rats was not influenced by the depression of NPY expression after EA during early puberty. Conclusion:The results demonstrated that repeated low frequency EA was an effective method on down－regulating NPY expression in the hypothalamus and we inferred that NPY was not the key role on regulating GnRH release in hypothalamus of common rats at early puberty stage.