To further explore the mechanism of slope protection by herbaceous plants in the loess region of northeastern Qinghai-Tibet Plateau, the Changlinggou catchment in Xining Basin was selected as the testing area. By designing two different slope shapes and selecting three herbaceous plants suitable for the local climatic conditions, and using the method of artificial rainfall simulation based on the field experimental area, the distribution and transformation of slope soil hydrological parameters (soil infiltration, soil moisture content) were analyzed first, then characteristics of soil water infiltration and its main influence factors on the slope of planting herbs were discussed. Finally, the process of soil water infiltration on the slope was simulated and evaluated. The results showed that the runoff generation time of the terraced slope planted with Elymus nutans in the area was the latest, and the maximum runoff occurred in straight bare slope, and the maximum stage cumulative runoff was 17 730 mL when the artificial rainfall time was 40~45 min. The average stable infiltration rate of the six different types of slope in the region from large to small was terraced slope planted with E. nutans (0.519 mm/min), straight slope planted with E. nutans (0.423 mm/min), straight slope planted with Elymus sibiricus (0.422 mm/min), straight slope planted with Agropyron trachycaulum (0.318) mm /min), terraced bare slope (0.321 mm/min), straight bare slope (0.192 mm/min). The increase of soil moisture content at 0—50 cm below the surface of the slope planted with E. nutans and E. sibiricus were relatively the highest, indicating that planting herbs was conducive to the internal water infiltration of slope soil. On this basis, Horton model, Kostiakov model and general empirical model were used to simulate moisture infiltration on slope. The results showed that Horton model and general empirical model were more suitable for fitting soil moisture infiltration on straight slope. While Horton model was more suitable for fitting soil moisture infiltration process on terraced slope. Pearson correlation analysis showed that soil organic matter and vegetation coverage were the main factors influencing slope infiltration characteristics in the testing area. And initial infiltration rate was significantly and positively correlated with soil organic matter content (R² was 0.986). And an extremely significant correlation between vegetation coverage and stable infiltration rate was identified (R² was 0.997). The results of this study had theoretical research value and practical guiding significance for the scientific and effective prevention and control of soil and water loss in alpine and semi-arid areas, and for the study of vegetation types and slope shape soil and water conservation capacity.