The invention discloses a sodium-modified illite-montmorillonite mixed-layer clay. The technical scheme is as follows: the sodium-modified illite-montmorillonite mixed-layer clay is composed of illite-montmorillonite mixed-layer clay, magnesia, sodium carbonate, instant sodium silicate, polyvinyl alcohol, hydroxypropyl methylcellulose and sodium acid pyrophosphate. The sodium-modified illite-montmorillonite mixed-layer clay materials are input into a mill and milled, and the milled powder illite-montmorillonite mixed-layer clay is the sodium-modified illite-montmorillonite mixed-layer clay. The sodium modification can enhance the water absorptivity, colloid index, expansion coefficient, colloid viscosity, cation exchange capacity, and dispersivity and suspension percentage in an aqueous medium of the illite-montmorillonite mixed-layer clay. The sodium-modified illite-montmorillonite mixed-layer clay has the characteristics of favorable thixotropy, favorable lubricating property, favorable heat stability, higher plasticity and higher binding property. The sodium-modified illite-montmorillonite mixed-layer clay is suitable for papermaking, cosmetics, plastics, rubber, paints, ceramics, textiles, cable insulation materials and firefighting materials.