Artificial sulfur (S) and nitrogen (N) addition experiments often fail to accurately simulate acid deposition in terms of type, composition, intensity, frequency, and duration, potentially leading to biased estimates of deposition impact on plant diversity. Consequently, studying plant diversity patterns around acid emission sources provides a more reliable alternative. Yet, this approach remains understudied in field research, particularly in saline-alkaline regions where high soil buffering capacity may attenuate plant sensitivity to acid deposition. Therefore, we investigated plant functional diversity (PFD) and analyzed its influencing factors in a desert coal-mining region in northwestern China characterized by high pH, abundant CaCO3 content in soils, and increasing acid deposition. The plant communities were characterized by high leaf thickness, low specific leaf area, and limited leaf total carbon (C) and N concentrations, indicating the preference of the plant communities for a slow investment-returning ecological strategy in the study region. In this context, leaf traits (e.g., thickness and total C and N concentrations), rather than PFD, played a major role in stabilizing plant communities. The intensity of S and N deposition had no effect on PFD. In contrast, exchangeable cation (BC) deposition directly reduced the functional richness, functional dispersion, and the Rao's indices, possibly by exacerbating soil salinity and alkalinity in the study region. Our findings indicate that PFD is mainly influenced by BC deposition in saline-alkaline coal-mining regions. Therefore, the potential risk of BC deposition, which accompanies acid deposition, posed on plant diversity should not be overlooked in these regions.