The effect of replacement of Portland cement by ground limestone as well as its specific surface Blaine (SSB) on the physical-mechanical properties of fresh and hardened cement paste is studied. The binder was composed of cement and limestone, which was prepared by eight replacement levels of limestone powder (0,5,10,15,20,25,30 and 35%) of binder by mass and four levels of SSB (300,600,800 and 1000 m2/kg). Test results demonstrated that the water requirement of normal consistency and the setting times(initial and final) decreased obviously as the replacement level of limestone powder increased and the extent of reduction was noticeable with the increase of SSB of limestone powder. The compressive strength of mortar incorporating different replacement levels and various SSB of limestone powder increased steadily with ages. The compressive strength decreased with the increase of replacement level of limestone, while as increased with the increase of SSB at the same replacement level and ages. The SSB influence factor was created to describe the effect of SSB of limestone powder on the compressive strength. The strength activity index of limestone powder concerning the replacement levels, SSB of limestone powder and mortar ages was established. The grade of limestone powder was suggested in order to reasonable utilization.