Abstract: The nano-alumina coating was prepared by suspension plasma spraying under atmospheric conditions, and the effect of nano-Al₂O₃ suspension concentration on forming of plasma spraying coating was studied by scanning electron microscopy and theory analyses.The results show that the concentration of nano-Al₂O₃ suspension has a significant influence on the size of droplet, the enthalpy needed for spraying suspension, the roughness of coatings surface and the microstructure of coatings.Low concentration of the suspension is beneficial for fine nanostructures coatings, which means low spraying efficiency.The optimized concentration of nano-alumina suspension is between 5%(wt) and 10%(wt).