Abstract: The contents of different particle sizes in soil are one of the main factors that affect the soil-water characteristic curve. It is of great practical value to study and analyze the seepage and strength problems of the unsaturated soil. In this paper, taking the laterite in Jiangxi Province as the research object, the soil samples having different contents of coarse and fine particles are prepared in five groups. And some studies of the fractal characteristics and fractal dimension D of the fractal theory are carried out on the basis of the fractal theory. The soil-water characteristic curves of soil samples are measured by filter paper method, and their characteristic values have been obtained. Then, the relationship between the characteristic values and the fractal dimension D is discussed and analyzed. The relevant testing with analysis results shows that for the soil-water characteristic curves with different particle size distributions, the greater the soil matrix suction of the soil samples with the same volume moisture content, the greater the fine soil matrix suction. The soil samples with different soil particle sizes have better fractal characteristics. It is feasible to analyze the influences of the particle size on the soil-water characteristic curves by the fractal dimension D. The quantitative indexes of the gradation of grain, C_u and C_c, show the law of increasing first and then decreasing with the increase of the fractal dimension D. And the fractal dimension D will decrease with the decrease of the fine soil content, and both the inlet values and the residual matrix suction values will increase with the increase of the fractal dimension D.