The objective of this study was to investigate the species diversity of herbaceous plant communities in forests regarding changes due to temperature increases, and the spatial distribution pattern at varying elevations and latitudes in a warming climate. Adhering to a latitudinal gradient, Guancen Mountain in the northern section of the Luliang Mountains and Wulu Mountain in the southern section of the Luliang Mountains were selected as study areas. Three plot categories [control, low temperature increase (OTC1), and high temperature increase (OTC2)]were set at different altitudes (high, medium, and low) in each of the study areas. During the vegetation growth season in 2017, plant diversity, frequency, coverage, and height were investigated to calculate species diversity indices (Simpson index, Shannon index, Pielou index, and Patrick index). An S-THB-M008 air temperature probe with an RS3-B radiation shield was set up at a height of 20 cm above ground level to measure ambient temperature. Our data revealed that the herbaceous species diversity in the forest community of the Luliang Mountains exhibited a "v-shaped" pattern depending on elevation (i.e., the lowest species diversity was found in the middle elevation). Altitude effects were most strongly correlated with the Simpson index (R²=0.1711), and the effects of the altitude gradient on diversity indices were highly significant (P < 0.01). Additionally, species diversity increased with latitude, and latitude effects were most correlated with the Simpson index (R²=0.1221, P > 0.05). This is followed by the Shannon index (R²=0.0807), the Pielou index (R²=0.0785), and the Patrick index (R²=0.0382). In response to increasing temperatures, each diversity index initially decreased, but then increased, with an overall downward trend (P > 0.05). Thus, increasing temperatures may decrease the plant species diversity of herbaceous layers under the forest canopy. Among species diversity indices, the Simpson index produced the strongest correlation of temperature effects (R²=0.3374, P > 0.05). Moreover, under simulated warming conditions, the Simpson index, Shannon index, and Patrick index of herbaceous species in Wulu Mountain exhibited a decreasing trend. In contrast, the Pielou index increases first and then decreases. In comparison, the Simpson index, Shannon index, and Pielou index of herbaceous plants in Guancen Mountain increased at first and then decreased, whereas the Patrick index increased. Overall, continued warming will decrease species diversity at lower altitudes of the Luliang Mountains. At moderate altitudes, species diversity will first decrease and then increase with rising temperatures. At relatively high altitudes, moderate warming will increase species diversity, but continued warming will negatively affect species diversity. Moreover, the effect of the altitude gradient on plant species diversity in the understory herbaceous layer was highly significant (P < 0.01). In Guancen Mountain, different treatments showed a significant effect on the Pielou Index (P<0.05). However, in other plots, different treatments did not significantly affect plant species diversity. The diversity of plant species was least affected by the combination of high gradients and different treatments. Therefore, the effects of warming on the diversity of herbaceous species in the forest community of the Luliang Mountains exhibit a decreasing trend with elevation.