Abstract: Based on two highways in Aksu prefecture of Xinjiang, four typical diseased sections are selected to excavate test pits on the basis of investigating bulging diseases of highways, the damage of structure layer pavement is observed, the salt content, mineral composition and pH value of base and subgrade fill are sampled and tested, and the mechanism of pavement diseases of the two highways is analyzed. The results show that the ions in the base course of Highway A (Provincial Highway) are mainly ${\text{SO}}_{\text{4}}^{\text{2}-}$ and ${\text{Ca}}_{}^{\text{2+}}$, so a chemical reaction takes place and Ettringite is formed. The content of ${\text{Ca}}_{}^{\text{2+}}$ in the base course of Highway B (National Highway) is high, and it also contains a certain amount of ${\text{SO}}_{\text{4}}^{\text{2}-}$ and ${\text{CO}}_3^{\text{2}-}$, so a chemical reaction takes place and Wollastonite gypsum is formed. In addition, the high temperature in summer and the alkali content in cement exceed the standard, accelerate the occurrence of two kinds of sulfate erosion. Finally, according to the mechanism of the two highway diseases, the preventive measures for bulging diseases of highways in the sulfate saline soil areas are put forward.