Abstract: To develop similar materials needed by the water-air coupling simulation test in research on reservoir construction in karst depressions, four groups materials with different particle size gradations were designed with sand, ordinary cement and gypsum as raw materials.The permeability, pore distribution and percolation characteristics of four groups of similar materials with different particle gradations were analyzed by rock low permeability test technology and nuclear magnetic resonance analysis technology.The results show that the permeability of similar materials increases linearly with the increase of particle gradation fractal dimension in the range of fractal dimension Df=1.68 ～ 2.31.In the four groups of samples, with the increase of fractal dimension, the total amount of pores in the material increases, the pore size distribution is more concentrated, and the corresponding main control pore size decreases.As the fractal dimension increases, the gray threshold increases, the percolation threshold decreases, and the percolation is more prone to happen.Based on the measured permeability, the permeability calculation model of the similar material is established, and the calculated value is in good agreement with the measured value.The research results have been successfully applied to the model test of karst depression and achieved remarkable results, which provides a material basis for further study of water-air interaction.