The invention provides a device and method for measuring the etching-resistant performance of a soil slope under the rainfall flushing condition. The device comprises an external cylindrical support frame, an internal cylindrical support frame, a metal square net with meshes, a vertical connecting support frame, a container in a shape like a Chinese character 'ao' and a balance, wherein a transverse connecting support frame is arranged on the top of the external cylindrical support frame along the radial direction of the external cylindrical support frame; the internal cylindrical support frame is inserted from the top of the external cylindrical support frame and is fixedly connected with the external cylindrical support frame through the transverse connecting support frame; the vertical connecting support frame is arranged inside the internal cylindrical support frame and moves along the axial direction of the internal cylindrical support frame; the external cylindrical support frame covers the outside of the balance; the container in the shape like a Chinese character 'ao' is arranged on the balance; the metal square net with the meshes is arranged at the bottom of the vertical connecting support frame and is arranged in the container in the shape like a Chinese character 'ao' in a suspended way. The device and the method have the advantages that laboratory equipment is effectively used for evaluating the anti-erosion performance of the soil slope; the field experiment work load is reduced; the cost is reduced.