Abstract: This paper aims to study the effect of gradation on the compaction and strength characteristics of coal gangue subgrade filler. It takes the coal gangue collected from an abandoned coal mine in Xiangtan of Hunan Province as the research object. It studies the gradation effect of the compaction and strength behaviors for coal gangue subgrade filler using large vibration compaction experiment and large-scale triaxial test. Based on the gradation equation of fractal model, the limit of well gradation is captured, and the advantages of using this gradation equation for designing gradation are analyzed. Moreover, the gradation has great influence on the compaction and strength of coal gangue subgrade filler. With the increase of fine particle content, the maximum dry density and deviatoric stress first increase and then decrease, which reflects the existence of an optimal range of particle gradation for coal gangue subgrade filler. On this basis, the optimal gradation ranges of coal gangue subgrade filler is obtained. In addition, the test results show that the optimal gradation ranges of coal gangue subgrade filler obtained by large-scale triaxial test and vibration compaction experiment are basically the same. Considering the high cost of large-scale triaxial test, the vibration compaction is recomended to obtain the experiment optional gradation.