In order to improve the stability of highway slope with earth-rock and expand the application of geonet, a large of rainfall simulation tests were carried out by rainfall simulation equipment for slopes of different gradients protected by composite geonet, three-dimensional geonet and single-layer geonet. The rainfall, the area of soil erosion, the amount of soil erosion, the modulus of soil erosion and anti-erision time with different protection measures and slope gradients were analyzed. As a result, the earth-fixing performance of three kinds of geonets is showed. The model between cumulative the area of soil erosion and time with a certain slope is established. And then different kinds of geonets should be appropriately applied to the different conditions. Thus it can be seen that the application conditions of different kinds of geonets provide a new research approach for the soil erosion of slope with earth-rock.