In this paper, Y2O3-Al2O3-ZrO2 nano-ceramic coatings were prepared on 316L stainless steel substrate at 600°C for 0.5 hour by sol-gel method, using Y(NO3)3•6H2O, ZrO(NO3)•2H2O and Al(NO3)3•9H2O as raw materials, hexamethylenetetramine as catalyst. Phases and morphology of these coatings were characterized by XRD, SEM and EDS. Effect of heat treatment temperature on microstructure of the coatings was studied. Y2O3-Al2O3-ZrO2 coatings with grain size about 50nm tightly integrated with metal substrate after densely sintering at 600°C. The grain sizes have grown up with increasing temperature.