Nanometer calcium carbonate (nano-CaCO3) is an inorganic material that does not have the rheological properties of a magneto-rheological fluid (MRF) but has some effects on the sedimentary stability and rheological properties of MRF. The MRF was prepared by adding nano-CaCO3 to improve its comprehensive and practical properties. The results showed that, with an increase in the amount of nano-CaCO3, the sedimentary stability of MRF would be improved. The off-state viscosity of MRFs increased with an increasing amount of nano-CaCO3. The shear stress of MRF was decreased slightly by adding nano-CaCO3. To some extent, the comprehensive and practical properties can be improved by adding a certain amount of nano-CaCO3. However, there is also certain localization that properties of MRF are improved by adding Nano-Inorganic Materials in the high temperature environment.