Commercial nano crystalline TiO2 Powders were used to fabricate coating layers, using plasma spray coating technique. The reactivity of photocatalyst of the plasma sprayed coating layers was characterized depending upon the different particle sizes of the starting TiO2 powders. The microstructures of the starting powders and the plasma sprayed coating layers were examined by TEM and SEM, respectively. Also the cross sectional areas of TiO2 coating layers were observed by SEM. The phases of the starting TiO2 powders and the plasma sprayed coating layers were analyzed by x-ray diffraction method. Surface roughness of the surface coating layers and microhardness of the cross sectional areas of coating layers were measured. It was found that phase transformation from anatase to rutile occurred, and the melted splats are all rutile, and unmelted nano particles were anatase. These unmelted particles of the anatase phase onto the melted splats of the rutile phase may play an important role of the reactivity of TiO2 photocatalyst of the plasma sprayed coating layers.