Abstract: In order to develop a kaolin ore resource in Yunnan Province reasonably and efficiently,two reducing agents, sodium disulfite and urea sulfur dioxide,were used to carry out whitening tests based on the analysis of ore properties. For kaolin samples with particle size of -0. 020 mm,the optimum bleaching conditions of urea sulfur dioxide were determined as pulp concentration of 20%,urea sulfur dioxide content of 2. 0%,pulp pH value of 13,oxalic acid content of 5%,reaction temperature of 30 ℃ ,reaction time of 20 min. Under the conditions,the Fe2O3 content of kaolin decreases from 0. 95% to 0. 70%,the iron removal rate reaches 26. 32%,and the natural whiteness increases from 65. 0% to 83. 5%. Compared with sodium disulfite,iron removal rate increased by 11. 58 percentage points and natural whiteness increased by 9. 1 percentage points. When urea sulfur dioxide is heated or catalyzed by alkali,strong reducing hyposulphuric acid is produced. Hyposulphuric acid reduces insoluble iron in kaolin to soluble ferrous iron and then removes it,thus improving the whiteness of sandy kaolin. Compared with sodium disulfite,urea sulfur dioxide has good iron removal effect,stable chemical properties and less environmental pollution. It can be used to remove iron and whiten kaolinite of the same type.