The invention relates to a rare earth element (RRE) tracing method for the sediment transporting capacity of water erosion in a sloping field. The rare earth element tracing method comprises the steps: arranging an RRE tracing element consumption and a sloping field, and calculating the sediment transporting capacity by applying an REE concentration. According to the RRE tracing method, a response relationship between a sediment runoff and a length of the sloping field on the basis of an RRE method is only established, and the sediment transporting capacity under any hydrodynamic condition can be calculated. According to the RRE tracing method disclosed by the invention, the sediment runoff of any section of the sloping field can be conveniently and rapidly estimated by only arranging different RREs on the sloping field, and the accuracy and the convenience of obtaining sediment runoff data with space distribution characteristics are improved.