Ossification of the ligamentum flavum (OLF) is characterized by a process of ectopic bone formation in the ligamentum flavum. The definitive pathophysiology of OLF still remains unclear, but the epigenetic m6A modification plays an important role in OLF. In addition, no studies have reported the function of ALKBH5 in OLF development. In this study, we investigated the function of the m6A demethylation enzyme ALKBH5 in OLF. To evaluate the function of ALKBH5, OLF tissues and normal ligamentum flavum tissues were collected. In vitro methods, including HE, IHC and western blotting assays, were used to evaluate the association of ALKBH5 with OLF. In addition, we verified the effects of ALKBH5 on osteogenesis using alizarin red and ALP staining. MeRIP q-PCR was performed to investigate the methylation level of BMP2. Moreover, the mechanism of ALKBH5-mediated regulation of the ossification of the ligamentum flavum cells through the AKT signaling pathway was also verified. The present study showed that the expression of ALKBH5 increased in OLF tissues. The overexpression of ALKBH5 increased the expression of osteogenic genes and promoted the ossification of ligamentum flavum cells. Furthermore, BMP2 was significantly enriched in the ligamentum flavum cells of the anti-m6A group compared with those of the IgG group. The overexpression of ALKBH5 led to the activation of p-AKT, and BMP2 was regulated by ALKBH5 through the AKT signaling pathway. ALKBH5 promoted the osteogenesis of the ligamentum flavum cells through BMP2 demethylation and AKT activation. ALKBH5 was shown to be an important demethylation enzyme in OLF development.