Grassland vegetation plays active and important role in conserving soil and water, particularly in the eco-environment construction on Loess Plateau. On the basis of reviewing and analyzing the past and present situation of the effect of grassland vegetation for conserving soil and water, the relationships between vegetation coverage and soil and water loss, between vegetation and runoff coefficients, the improvement of root system of grassland vegetation on anti-scourability and anti-erodibility of soil were induced and summarized. The existed problems including the impact of grass coverage on runoff resistance characteristics, the maximum capacity of grass in conserving soil and water, the mechanism of grass in conserving soil and water, the best position of grass distribution on sloping surface and the impact degree of grass coverage on gully erosion when the grass resumed on the sloping surface were discussed. Some blanks existed in the present research field, including the impact of dead grass roots on soil organic matter content, shear stress and the water stability of soil aggregate, the quantitative calculation of benefit of grass in conserving soil and water are pointed out. Also the future directions of research in these fields were discussed, so that the role of grassland vegetation in conserving soil and water can be evaluated scientifically and provide some references for the present and future eco-environment construction in this area.