Investigating the effect of the aggregate gradation on the material properties of cemented rockfill is significant for the green mining, economic benefit and engineering safety. Consequently, the ultrasonic test, uniaxial compression experiment and acoustic emission (AE) monitor on cemented rockfill were carried out, for which the aggregate satisfied Talbot gradation. The dilatancy behavior and AE characteristic of cemented rockfill under load were investigated. The damage in the internal structure under compression was revealed by the deformation and AE signals of cemented rockfill. The effect of the Talbot index on the ultrasonic pulse velocity (UPV) and the strength parameters such as stress of dilatancy onset and uniaxial compressive strength (UCS) of cemented rockfill was analyzed. The mechanical properties of cemented rockfill materials were evaluated by the establishment of the relation between the UPV and the strength parameter. The results show that The difference between the stress of dilatancy onset and the UCS, the deformation performance and the activity of AE signals during dilatancy are positive correlated with the Talbot index of aggregate in cemented rockfill. The relation between the UPV and the strength parameters (stress of dilatancy onset and UCS) of cemented rockfill can be characterized by the positive linearity, and the UPV is also suitable for characterizing the stress of dilatancy onset of cemented rockfill material. The cubic polynomial is more suitable for describing the relations between the parameters of strength and UPV and the Talbot index of aggregate than the quadratic polynomial, and the Talbot index with optimal aggregate gradation reflected the maximum strength of cemented rockfill material should be around 0.45–0.47.