Objective To investigate the expression level of BAX gene of acute promyelocytic leukemia (APL) and its regulation mechanism. Methods The expression level of BAX gene of patients with APL was detected by the real-time PCR. The enrichment of PML/RARα fusion protein at the promoter region of BAX gene was detected by the chromatin immunoprecipitation (ChIP). The expression level of BAX gene and protein after the drug induced degradation of PML/RARα was detected by the real-time PCR and Western blotting. Results The expression level of BAX gene in APL samples was significantly low. PML/RARα fusion protein directly bound the promoter region of BAX gene. The expression level of BAX gene significantly increased after PML/RARα was induced to degrade. Conclusion PML/RARα inhibits the expression of BAX gene in APL by directly binding to the promoter region of BAX gene and inhibiting the activity of promoter.