Based on the close packing theory, the MAA model and Fuller maximum density theory were used to select the optimal gradation of aggregate. The orthogonal test method was used to determine the optimal mix ratio of epoxy concrete, and the mechanical properties evaluation and microscopic analysis were carried out. The results show that the close packing porosity of aggregate is significantly reduced after gradation optimization, and the most closely packed porosity is only 22.23%. The bone-binder ratio has a significant influence on the splitting tensile strength of epoxy concrete, and cement is suitable for incorporation into epoxy concrete as a filler. The cube compressive strength of epoxy concrete increases slightly with the increase of age, and is closely related to the curing degree of epoxy resin. When the epoxy resin is completely cured, the cube compressive strength basically does not change with the age. The mechanical properties of epoxy concrete after gradation optimization are improved, the cube compressive strength is increased. Through SEM microscopic test analysis, it is found that the internal harmful defects of epoxy concrete after gradation optimization are significantly reduced, the system is dense and uniform, and the internal bonding force becomes stronger.