[en] Highlights: • CaPh/ZrO_2 coating on AZ91D has been originally prepared by electrolytic deposition. • ZrO_2 dense interlayer enhances the adhesion of CaPh top coating and the corrosion resistance. • The top CaPh layer enhances cell adhesion and cell proliferation. • With greater bioactivity, CaPh/ZrO_2-coated specimen has potential as biodegradable implants. - Abstract: A composite coating of calcium phosphate/zirconia (CaPh/ZrO_2) has been applied to the AZ91D magnesium alloy through electrolytic and annealing methods for enhancing corrosion resistance and bioactivity. The intermediate ZrO_2 layer plays an important role in enhancing the adhesion strength of top CaPh layer on AZ91D as the condensation of hydroxyl bonds in Zr(OH)_4 precursor, also leading to the reduction of corrosion current density down to two orders of magnitude. On the other hand, the top CaPh layer enhances much more cell adhesion and proliferation, compared with the reduced cell number on the uncoated AZ91D due to its high corrosion rate.