Due to the poor adsorption performance and extreme toxicity of the heavy metal cadmium ion, it is of great practical significance to explore an efficient adsorption material for cadmium immobilization. In this paper, the modification by grafting sulfhydryl silane onto kaolinite was investigated and confirmed by infrared spectroscopy which proved that sulfhydryl groups were successfully introduced onto the surfaces of kaolinite. At the same time, silane modification did not cause the change of kaolinite in the crystal structure. Batch experiments were conducted to investigate the adsorption characteristics of kaolinite and modified kaolinite (K-SH) for Cd²⁺ under different conditions, mainly including pH and adsorption time. The adsorption kinetics of cadmium ions by the two materials is in agreement with the pseudo-second-order kinetic model. Nevertheless, the relevant adsorption isotherm equation showed a good fitness with the Langmuir model. The calculated maximum adsorption capacity of K-SH is 4.375 mg/g, which is 20 times higher than that of original kaolinite. The modified kaolinite grafted with sulfhydryl groups provided a large number of new adsorption sites on its surface, thus significantly improving the capacity of adsorption and immobilization for cadmium ions by coordination and complexation. It is therefore held that sulfydryl organic silicane-grafted kaolinite is a promising soil remediation material.