Joint quality between two layers in RCC(roller compacted concrete) has direct effect on the safety of RCC dam, and the different time intervals between two layers roller compact and the different layers surface treatment are the key of connection. This paper discusses the influence of the different time intervals of twolayer roller compact and the different layer surface treatment on shear properties of combination between RCC layers. The results show that: ① shortening the time interval of twolayer roller compact as much as possible is the key to ensure the RCC quality of twolayer surface connection; ② each layer surface doesn’t need treatment, on which one may directly pour so as to make RCC into an unity; ③ some treatment manners of layer surface in the period between early setting and final setting and after final setting are proposed. The finding provides important basis for RCC dam construction of Pengshui Hydropower Station.