Objective To study the effects of heroin on the development and brain Bax expression in embryonicrat brain tissues. Methods Wistar rats were randomly divided into a control group or heroin administration groups (low,medium, and high dose groups). On the 7th day, 16, 32, and 64 mg/ kg of heroin were administered to the low, medium,and high dose groups, respectively, and heroin was continuously administered for 9 days. The effects of heroin onmorphological development of embryonic rats were measured, and the expression levels of Bax in embryonic brain tissueswas detected using enzyme-linked immunosorbent assay (ELISA). Results The total numbers of living embryos in thelow, medium, and high dose heroin groups were decreased by 27. 27%, 37. 12%, and 48. 48%, respectively, comparedwith the control group ( P < 0. 01). Bax expression levels in embryonic cerebral tissues of the low, medium, and high doseheroin groups were increased by 11. 41%, 47. 06%, and 83. 74%, respectively, compared with the control group ( P <0. 05; P < 0. 01). Bax expression levels in the embryonic cerebellar tissue were increased by 17. 16%, 52. 96%, and90. 01%, respectively, compared with the control group ( P < 0. 05; P < 0. 01). Conclusions Heroin inhibitsmorphological development in embryonic rats, and this inhibitory effect increases with increasing doses of heroin. This effectmay be caused by the heroin-induced upregulation of Bax expression in embryonic tissues and organs.