Abstract: In recent years, due to the change of natural environment and the influence of human engineering activities, the occurrence probability of geological disasters such as soil erosion and landslides have been increasing. These geological disasters bring some damages to people's living and productive activities. Methods of soil fixation and slope protection by vegetation can prevent and control the geological disasters. The soil fixation and slope protection by vegetation can be mainly reflected in two aspects: hydrological effect by the stems and leaves of plants and the mechanical effect by the root of plants. Hydrological effect includes rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage, and plant residues and surface runoff retardation effect by plant above-ground residues. The mechanical effect includes reinforcement effect by fibril roots, anchorage effect by taproots, and traction effect by horizontal roots. The paper highlights the research status of hydrological effect and mechanical effect. For hydrological effect, content such as rainfall interception effect and rainfall reallocation effect by plant stems and leaves, effect of reduction in raindrop splash erosion by foliage and so on are the key contents. For mechanical effect, the theoretical models for the additional cohesion force due to the presence of roots, the interaction between plant roots and the surrounding soil matrix and the numerical simulation methods for the mechanical effect of the slope protection by vegetation are emphasized. In addition, the development tendency of soil fixation and slope protection by vegetation has been predicted. For hydrological effect, a further investigation on the influence of water migration among atmosphere-soil-plant on slope stability is desirable. For the theoretical models of root-soil composite system, a further exploration on the working conditions for which the Wu-Waldron-Model and Fiber-Bundle-Model can be suitable, is necessary. For the numerical simulation methods, effort is needed to explore a model that meet the real condition. With the establishment of numerical model, the parameters such as the root architecture features, root length and so on, as well as these parameters influencing on the calculation results should be taken into account systematically. For the engineering practice, a further study on the application of slope protection by vegetation should be performed to explore the application and maintenance of slope protection by vegetation in different geological and climatic conditions to ensure that slope protection by vegetation can play an eminent role in engineering practice as well as embodying the combination of hydrological effect, mechanical effect and landscape effect.