The nurse effects are critical for maintaining biodiversity and ecosystem functions in arid and semiarid areas. However, whether promoting or competing interactions dominate in regions with high biotic and abiotic stress remains unclear. In order to investigate the effects of artificial Caragana intermedia forest on the community structure, species diversity and functional group distribution of herbaceous plant communities under its canopy in desert steppe in Yanchi County, Ningxia, the estern side under the canopies (SE), western side under the canopies (SW) and the gaps (Gap) were selected as the research plots. The vegetation characteristics, microclimate and soil factors were studied. The results showed that:(1) 12 plant species were identified in each of the 3 microhabitats. The dominant species in SW, SE and Gap were Agropyron mongolicum, A. mongolicum and Pennisetum centrasiaticum, A. mongolicum and Lespedeza potaninii, respectively, and the important values varied from 19.35 to 43.07. (2) Compared with Gap, the average height of plant communities for SW and SE increased by 41.06% and 81.75%, and the aboveground biomass increased by 40.88% and 38.73%, respectively. There were no significant differences in vegetation coverage among SW, SE and Gap (P>0.05). The aboveground biomass of the gramineous plants occupied 67.10% and 58.40% of the total aboveground biomass and the important values of the gramineous plants were 62.17 and 66.79 in SW and SE respectively, which were significantly higher than that in Gap(P<0.05). (3) The canopy effects of C. intermedia increased the richness index of herbaceous plants, the species richness index of SW was 8.8, which was significantly higher than that of Gap (P<0.05). There were no significant effects of C. intermedia on Shannon-Winner index, Simpson index and Pielou index of herbaceous plant communities, which ranged from 1.620 to1.756, 0.701 to 0.730 and 0.775 to 0.878 (P>0.05). (4) Redundancy analysis showed that soil temperature, relative air humidity and soil organic carbon were the main factors affecting herbaceous plant species diversities and biomass, and their explaining rates were 42.70%, 11.70% and 8.80% respectively. Based on the results of this study, the C. intermedia had a certain conservation effect on herbaceous plant communities under its canopies, especially Gramineae. This effect was mainly caused by the improvement of the microclimates such as relative air humidity, soil temperature and soil organic carbon under the canopies of C. intermedia, which provides favorable conditions for the growth and development of herbaceous plant. The nurse effect of C. intermedia on herbaceous plant is of great significance to the protection and restoration of the desert steppe ecological environment.