Effect of Supersonic Particles Deposition processing parameters on porosity and bonding strength of Al-Si coating on the surface of ZM5 Magnesium alloy was studied. The result shows that the porosity rates of Al-Si coating are all below 0.6% and the bonding strength is all above 35MPa. With air pressure increasing, the porosity of Al-Si coating reduces to below 0.3% and the bonding strength increases to above 40MPa. With spray distance increasing, the average percent voids of Al-Si coating tends to increase and the bonding strength is better between 160mm and 200mm. The minimum porosity and the maximal bonding strength of the coating can be reached when the speed of feeding powders is at 6r/s.