In this paper, alumina (Al2O3) slurry properties and spraying drying conditions were optimized by orthogonal experiment for preparing the dense and spherical alumina feedstock. The feedstock was carried in a moving gas stream and deposited on the stainless substrate by atmospheric plasma spray (APS).The phase composition and microstructure of feedstock and as-sprayed coatings were studied by XRD, SEM and TEM. In addition, the porosity, surface roughness and micro hardness of as-sprayed coatings were also investigated. The results showed that Al2O3 powder content in slurry was the most influential factor for the particle size and morphology of feedstock and most of α-Al2O3 existing in the starting feedstock transformed into γ-Al2O3 during APS. Moreover, it was found that, using the feedstock prepared by optimized parameters, the as-sprayed coating had an average grain size of about 250 nm, with lower porosity of about 4 %, surface roughness Ra of about 1.94 μm, micro hardness HV0.3 of about 1000 under applied load 300 g.