Objective To solve the spraying problems of unsintered nanostructured agglomerates, retain more nano particles that resemble to the original powder in size and study the relation between nano structure features and arc current change when unsintered nanostructured agglomerates are deposited. Methods The deposition of unsintered YSZ spray dried agglomerates was carried out by extending the gun barrel. YSZ coatings with different nano structures were fabricated with the current of 150 A, 200 A, 250 A respectively. The microstructure, especially the nano structure feature change and phase structure were investigated via field emission scanning electroscopic and X-ray diffraction method. The average grain size of the as-sprayed coatings was evaluated through Debye-Scherrer formula. The Weibull analysis of Vicker`s microhardness under lower load was also adopted to analyze the character of the nanostructured coatings. Results Powders entered plasma jet via extended gun barrel and the deposition efficiency of unsintered agglomerates reached 21.2%~40.2%. The average grain size of the as-sprayed coatings was evaluated to be 44~56 nm. The content of the compacted and less infiltrated nano-zone reached the peak value of 37% with the arc current of 200 A. The nano zone exhibited different structures when the arc current was further increased or decreased, the characteristics of which could be further illuminated by Weibull analysis. Conclusion The gun configuration used in this study is effective in spraying unsintered agglomerates which are porous and weak bounded and reducing the average grain size of the as-sprayed coatings.