In order to evaluate the modification effect of nano-SiO2 (NS) and nano-CaCO3 (NC) on the basic properties of cement slurry. In this paper, the orthogonal test and electron microscope scanning test of cement slurry under different nanometer dosages are carried out. The effect of different factors on the basic properties of cement slurry and the mechanism of nano-materials on the modification of cement slurry were studied. The results show that water-cement ratio has the greatest influence on slurry specific gravity and setting time, followed by NC, and NS has the smallest effect; at the same time, water-cement ratio has the greatest influence on slurry fluidity and water release rate, followed by NS, and NC has the smallest. There is no significant difference in the influence of the two nano-materials on the specific gravity and setting time of cement slurries. However, there is a suitable blending value (0.5%) in NC for the effect of slurry water release rate and fluidity. The modification effect on cement slurry gradually decreases. The research results can provide experimental basis for the reasonable selection of parameters such as cement slurry water-cement ratio and the amount of nano-modified materials.