The radionuclide cesium (Cs) was solidified using magnesium silicate hydrate (M-S-H) cement. The influence of Cs+ on the reaction of the M-S-H gel system was evaluated by measuring the compressive strength and microscopic properties of the solidified body. By testing the impact resistance, leaching resistance and freeze-thaw resistance of the solidified body, the immobilizing ability of Cs+ by the M-S-H cement was analyzed. Results indicate that Cs+ only slightly affects the reaction process of the M-S-H gel system, and only slows down the transformation rate of Mg(OH)2 into the M-S-H gel to a certain extent. The M-S-H cement exhibits superior performance in solidifying Cs+. Both the leaching rate and cumulative leach fraction at 42 d were considerably lower than the national requirements and better than the ordinary Portland cement-solidified body. The curing effect of the M-S-H cement on Cs+ is mainly physical encapsulation and chemisorption of hydration products.