The invention provides a method and a system for determining a heavy metal migration trend in soil. The method comprises the steps of 1) selecting a soil area contaminated with heavy metals; 2) determining a test area in the area; 3) setting sampling points in the test area and sampling at the sampling points at different depths; 4) measuring the heavy metal content in each sampling point at different depths, averaging the measured heavy metal content to obtain the heavy metal content in real soil, the heavy metal content in the overground part and heavy metal content in underground part of each plant in the test area; and 5) comparing the heavy metal content in the overground part and the heavy metal content in underground part of each plant with the heavy metal content in the real soil to obtain the heavy metal migration trend. The method and the system provided by the invention can determine the heavy metal migration trend accurately, and provide reference data for obtaining plant species suitable for repairing the soil contaminated with the heavy metals and solving the problem that the soil contaminated with the heavy metals can not well match with the plant species for repairing the contaminated soil.