The invention discloses a soil remediation agent filling device in the technical field of soil remediation. The soil remediation agent filling device comprises a driving device, a rear box is fixedly installed on one side of the driving device, a hydraulic cylinder is fixedly connected to the top of the rear box, a guide block is fixedly connected to the output end of the hydraulic cylinder, a supporting plate is fixedly connected to one side of the guide block, a cavity is formed in the supporting plate, a pneumatic cylinder is arranged in the cavity, and the output end of the pneumatic cylinder is fixedly connected with a connecting plate. According to the device, large-area soil can be loosened, the working efficiency is improved, the labor intensity of workers is reduced, most of agents cannot be blown to the soil outside an outer box under the influence of wind power or vehicle speed, and the problems that agents are sprayed unevenly, and the local soil remediation capacity is poor are solved; and through cooperative use of supporting blocks, rotating rods, side plates, iron plates and iron hooks, the iron hooks can completely enter the loosened soil to stir the soil sprayed with the agents, and the remediation capacity is good.