Hydroxyapatite/collagen composite (HAC) was preliminarily fabricated by biomineralization, the bioactive poly(L-lactic acid)/HAC composite coatings were spin coated on AZ31 magnesium alloy using poly(L-lactic acid) solution mixed with HAC particles, the resultant materials and coatings were characterized in structure and properties, furthermore the in-vitro degradation behavior in 1.5-fold Hanks solution was investigated.The results show that HAC composite achieved chemical bonding between hydroxyapatite and collagen similar to natural bone, composite coatings on AZ31 magnesium alloy retained the bioactive functional groups of the componential materials and improved the corrosion resistance of Mg alloy, the mass fraction of HAC particles incorporated into the composite influenced the porous architecture and thus the corrosion resistance of the composite coating due to phase separation cause as well as volume concentration effects.Composite coatings curbed the sharp rising of pH value and inhibited the released Mg2+ from substrate to extensive degree, and the degradation behavior was supposed to be correlated to microstructure of the coating as well as the synergistic reactions among alkaline and acidic degraded products.