The invention discloses a remediating agent suitable for cadmium contaminated soil and a preparation method of the remediating agent. The remediating agent suitable for the cadmium contaminated soil is prepared from the following raw materials in parts by weight: 20-60 parts of sepiolite, 10-50 parts of lime, 5-35 parts of monocalcium phosphate, and 5-20 parts of plant ash; the average granularityof each material is 200 meshes. The method mainly comprises the following steps: grinding sepiolite powder into 200 meshes; modifying: modifying the sepiolite by maintaining microwave radiation under60-100 DEG C; mixing the modified sepiolite, lime, monocalcium phosphate and plant ash; packing to obtain the sepiolite-based remediating agent for the cadmium contaminated soil. The prepared sepiolite-based remediating agent is applicable to repairing of the cadmium contaminated soil and can obviously reduce the concentration of cadmium in soil leachate; the stabilizing rate is 99% or higher; the repairing agent is environmentally friendly, low in remediating cost, and high in operability.