Abstract： Taking the complexes of methoxy grafting kaolinite as precursors, kaolinite layers were peeled by the method of intercalation-stripping to get ultrafine kaolinite particles. Using Zhangjiakou kaolinite ore as comparative tests samples, the particle sizes of kaolinite ore samples and ultrafine kaolinite samples were tested by the methods of laser, image processing and resistance respectively. The results show that the three test methods can be used for kaolinite particle size test. The difference of the results is small, and the variation trend of particle sizes is consistent. The particle size of kaolinite ore distributes dispersedly, while that of ultrafine kaolinite distributes concentratedly. In the particle size test of Zhangjiakou kaolinite ore, the result of laser method is great, the result of resistance method is small, and the result of imaging method is in the middle, so the imaging method is preferred. In the particle size test of ultrafine kaolinite, the result of imaging method is great, the result of resistance method is small， and the result of laser method is in the middle, so the laser is preferred.

Keywords: kaolinite; particle size; laser method; imaging method; resistance method