The invention provides a soil activator for remediation of cadmium-contaminated soil as well as a preparation method and application thereof, and belongs to the technical field of soil pollution control and remediation. The soil activator is used in cooperation with soil remediation plants and is prepared from the following components in percentage by mass: 40-60% of phosphate fertilizer, 15-25% of phosphorus-potassium fertilizer, 15-25% of silicate, 1-5% of organic fertilizer and 1-5% of metallo-chelate. The preparation method for the soil activator is characterized in that the phosphate fertilizer, the phosphorus-potassium fertilizer, the silicate, the organic fertilizer and the metallo-chelate are mixed so as to obtain the soil activator. The soil activator is used in cooperation with sedum alfredii hance plants. The soil activator prepared through the method is used in cooperation with the sedum alfredii hance plants, so that cadmium metal in the soil can be effectively adsorbed, and remediation can be carried out on the soil contaminated by cadmium.