Slope protection with plant roots not only works effectively but also beautifies the environment. It has been used in engineering for a long time and it could be the trend of slope protection in the future. This paper studies the shear behavior of disturbed gravel sand soil with roots and without roots under different water content by using the direct shear test. The results show that, (1) The cohesion of the soil with roots decreased while the internal frictional angle increased under the same water content; (2) The shear strength of soil with roots decreased with the increase of water content. The paper also puts forward some suggestions in engineering application of plant roots in slope protection.