Red sandstone is widely used as a kind of engineering filler, and it is prone to disintegration under repeated dry and wet cycles in the natural environment, which causes a lot of engineering problems. The red sandstone in Zhuzhou area of Hunan Province was taken as the research object, the distribution of particle size and the variation of particle gradation after disintegration under dry and wet cycles were studied. The results showed that the gradation curve of red sandstone disintegration particles under the dry and wet cycle showed the anti-S-shaped. Disintegration characteristic of red sandstone was studied based on the optimized grading equation, and the applicability of the optimized grading equation to the grading description of disintegration particles was analyzed. The feasibility of the gradation parameters as a disintegration indicator was verified combined with the existing disintegration indicators, and the advantages were pointed out. The uniformity of particle grading after rock disintegration was also studied.