Magnesium (Mg), and its alloys have good potential for using in biomedical applications due to its good mechanical properties and biodegradability. However, the poor corrosion resistance and insufficient mechanical stability of Mg in biological fluids have limited its clinical applicability. As a result, surface modification techniques are being investigated to improve corrosion resistance for biomedical applications. In this study, a bioactive CaP film were deposited on the surface of the AZ31B magnesium alloy via anodization with SBF solution used as the electrolyte with and without ZrO2 Nanoparticles (NPs). The samples were evaluated and characterized in vitro to assess their degradation and cytocompatability behaviour via FE-SEM, electrochemical corrosion test, immersion test, and cell culture tests. The results indicate that the AZ31B Mg alloy surface anodized in SBF with and without ZrO2 NPs consists of CaP nanoplate leaf-like apatite structures and porous 3-D structures, respectively. The nanomorphology showed uniform growth on the anodized surface that had created the porous layer on the surface of the samples three days after immersion in the SBF solution. The formation of such nanostructures on the anodized sample could provide the implant materials with extra biocompatibility. Moreover, this unique deposited layer can improve the corrosion resistance and cytocompatability of the Mg alloys, which make it a promising material for use in biomedical applications.