Limestone and metakaolin partially replace cement can effectively reduce the carbon emissions of cement products. The rheological properties of fresh limestone-metakaolin-cement paste system were tested by Antonpa MCR 302 rotary rheometer. Simplex barycenter method was applied to limestone-metakaolin-cement mortar system. The rheological properties of mortar with different ratios were tested by Viscometer 5 concrete rheometer. The results show that the yield stress and the plastic viscosity of cement paste increase significantly with the increase of metakaolin content. However, with the increase of limestone, the yield stress and the plastic viscosity of cement paste increase first and then decrease. Changing the ratio of binders significantly affects the fluidity and the rheological parameters of mortar.