Abstract: In order to study the effect of nano-SiO2 on shear strength and rheological properties of cement grout, a series of direct shear tests were conducted under multiple constant normal loads for cement grouted samples with water-cement ratio of 1.0 and 3-day curing time. Then, the influence of nano-SiO2 on shear behavior and shear strength parameters(τp, c and φ) of samples was studied, and the rheological properties of grouts after adding super plasticizer were further studied. The results showed that with the increase of shear displacement, the shear stress increased gradually until the peak stress was reached, and then it appeared as strain softening stage. After the addition of nano-SiO2, the cohesion and internal friction angle of the samples were increased by 8.2 % and 4.1 %, respectively. The viscosity of grouts containing nano-SiO2 increased significantly. By adding 1.5 % super plasticizer, the fluidity of the grouts containing nano-SiO2 could be significantly improved, so as to obtain the grouts with high fluidity and permeability.