Abstract: In order to find the causes which affect the cleanliness of TiO₂ by sulfate process,the estima-tion method for cleanliness during the dispersity testing was studied.The result shows that the cleanliness is a key factor influencing the dispersity evaluation,while the coarse particles in the product are the main influencing factors to the cleanliness of TiO₂.According to the comparative analysis,the impurity parti-cles in the domestic TiO₂ mainly consist of Ca,Al and Si with the maximum particle size of 210 μm,while the main component of coarse particles in foreign titanium dioxide is TiO₂ with the size less than 30μm.The cleanliness and dispersity of TiO₂ can be improved by screening the coarse particles from the slurry after inorganic surface treatment.