The invention provides a red-mud-based one-step-process geopolymer grouting material and a preparation method thereof. A solid material of the grouting material comprises powder and an additive. The preparation method of the powder comprises the following steps: uniformly mixing red mud, an active aluminum-silicon source and a solid alkali activator, conducting heating to not less than 600 DEG C for calcining; and crushing the calcined material to the powder of the red-mud-based one-step-process geopolymer grouting material, wherein the activated aluminum-silicon source is one or more of blastfurnace slag, ash and silica fume, and the solid alkali activator is one or more of slaked lime, caustic soda and desulfurized gypsum. The grouting material can be directly hardened to obtain an one-step-process red mud-based polymer after mixed with water.