Micro-arc oxidation (MAO) coatings were prepared on ZL108 aluminum alloy in the Na2SiO3 electrolyte adding graphite micro-particles at different current densities (1, 5, 10, 15 and 20 A/dm2). The characteristics of MAO coatings were studied by SEM, EDS, XRD, eddy-current thickness meter and micro-hardness tester. The result showed that the thickening of MAO coatings led to the increase of the oxidation voltages with the increase of current density. The surface of MAO coatings was porous. The diameter of micro-pore and the size of sintering discs gradually increased. The relative counts of C and Si element on the surface of MAO coatings increased with the increasing of current density. The C element was uniform distribution on the surface of MAO coatings. The C element on cross-sectional of MAO coatings mainly concentrated on outer side. MAO coatings mainly consist of SiC, SiO2, θ-Al2O3, α-Al2O3. The SiC phase derived from the reactions of SiO2 with graphite. With the increase of current density, the MAO coatings hardness increased. MAO coatings prepared at 5A/dm2 exhibited the lowest corrosion rate.