Abstract: In this paper, in order to investigate the applicability of large particle size aggregate in asphalt concrete impervious panel materials, and to reduce the material costs while improving the mechanical properties of asphalt concrete, the maximum particle size Dmax of asphalt concrete aggregate in impervious layer was increased from 16mm to 26.5mm and 31.5mm. The optimal mix parameters of three groups of asphalt concrete with different maximum particle sizes are obtained through mix proportion tests. Additionally, splitting, uniaxial compression, tensile, and slope flow tests were conducted. The performances of the three groups of asphalt concrete with different maximum particle sizes were compared, and the impact of aggregate size on their properties was analyzed. The results demonstrate that the maximum particle size aggregate has a significant impact on both the mix proportion parameters and the properties of asphalt concrete. With the increase of the maximum particle size of aggregate, the gradation index increases, the specific surface area of aggregate decreases, and the asphalt-aggregate ratio decreases (reducing from 7.0% to 6.2%), thus effectively reducing the material cost; By properly increasing the maximum particle size of aggregate, it is helpful to improve the splitting strength (an increase of 4.02%) and compressive strength (an increase of 14.07%) of asphalt concrete, and reduce the slope flow value; However, when the maximum particle size of aggregate is too large, the tensile strength decreases (a reduction of 5.78%), the failure mode is mainly brittle failure, and the toughness and deformation adaptability of the material will be weakened. This study aims to provide a theoretical basis for the research on the applicability of large particle size aggregates in the impermeable layer asphalt concrete of pumped storage power station panels.