The invention provides an experimental device for simulating migration of microplastics in soil and an experimental method thereof. The experimental device comprises a drain tank and an experimental assembly, wherein the drain tank is provided with a drain outlet; the experimental assembly is arranged in the drain tank, the experimental assembly comprises an experimental tube arranged in the draintank and silica wool arranged a the bottom part of the experimental tube, and the experimental tube is further used for bearing sand positioned on the silica wool and the microplastics arranged on the sand; and an experimental solution is injected into the experimental tube from the top part of the experimental tube, so as to simulate a migration path of the microplastics in soil. The experimental device realizes the simulation of migration of the microplastics in soil, facilitates the experimenter to obtain experimental data on migration of the microplastics in the soil, and provides a theoretical basis for practical applications. At the same time, the experimental device for simulating migration of microplastics in soil has the advantages of being simple in structure, convenient in experimental operation, capable of being recycled, and low in cost.