The influence of granulated ground blast furnace slag(GGBS) on properties of fresh micro-fine cement(MC) paste was experimentally investigated. The results show that GGBS can dilute and lubricate the paste. It can also obviously increase the setting time of cement. Furthermore, with the increasing of flow velocity ([AKv-]_B) and grouting quantity (q_b), GGBS improves the groubility of MC paste.