300 nm-thick TiN thin films were deposited by reactive magnetron sputtering under different N₂flow ratios. Film surface morphologies were observed by atomic force microscope(AFM)and analyzed by fractal theory. The correlation between sputtering model and fractal dimension D_? was investigated. With the increase of N₂ flow ratio,the sputtering model of TiN film changes from metal model to transition model and to nitride model. Accordingly,D_? undergoes the decrease followed by slight increase.