Understanding the responses of herbaceous plant functional groups to environmental changes and their distribution pattern in a forest-steppe zone is helpful for clarifying the factors influencing different groups and for improving conservation strategies for herbaceous species diversity in the fragile landscape. A total of 184 sample plots (1 m * 1 m) were established and assessed using a stratified random sampling design in the Saihanba Nature Reserve, Hebei. Herbaceous plant species were divided into C_3 and C_4 functional groups. Twenty environment factors related to topography and climate were obtained from the ClimateAP (Climate Asia-Pacific) model and by utilizing GIS (Geographic Information System) spatial analysis techniques. The ecological niche model (MaxEnt) was adopted in predicting the potential distribution of both C_3 and C_4 plant functional groups. Our results showed that the area under the receiver operating characteristics curves (AUC) for the C_3 and C_4 were all over 0.8,indicating that the MaxEnt model had good predictive performance. The C_3 functional group had a large potentially suitable distribution range, whereas the C_4 functional group had a relatively small distribution in the study area, accounting for 61.99% and 19.12% of the total area,respectively. The main environmental factors affecting the distribution of C_3 included: extreme maximum temperature, mean winter snow, degree-days above 5℃,mean annual temperature,and mean temperature of the coldest month. The main environmental factors affecting the distribution of C_4 species included: extreme maximum temperature,degree-days above 5℃,mean annual temperature,mean annual precipitation, and mean winter snow. Accordingly,the results confirmed that C_3 species potentially occurred in cooler and wetter conditions, whereas C_4 species might tend to potentially occupy warmer and drier locations in the study area. The distribution range and area of C_4 herbaceous species will probably increase in response to global climate warming.