With the increase in coal mining on Ordos Plateau, North China, pollution due to coal dust deposition has become an important factor that affects the growth and survival of local plant species. Hedysarum laeve Maxim. (Fabaceae), a dominant plant species on Ordos Plateau, was used to examine the effects of coal dust deposition on some photosynthetic and other physiological parameters during seedling growth. By conducting near-natural controlled experiments, we investigated the photosynthetic characteristics and seedling growth of H. laeve in response to different coal dust concentrations (0, 0.7, 1.6, 2.3, and 3.5 mg/cm²). The Li-6400XT Portable Photosynthesis System was used to measure the photosynthetic parameters of H. laeve leaves at different dates during the growing season of 2013. Simple correlation analyses were used to understand the relationships between coal dust concentration, photosynthetic parameters, and seedling growth characteristics of H. laeve. The results showed that: (1) stomatal conductance, internal CO₂ concentration, and leaf-to-air vapor presser deficit were significantly affected by increasing concentrations of coal dust, resulting in the decrease of net photosynthetic rate and transpiration rate, and (2) height, number of leaves, number of branches, and biomass of H. leave seedlings were negatively affected. Our study indicated that coal dust deposition negatively influences the seedling growth of H. laeve by blocking stomata and adversely affecting water and gas exchange processes and reducing light intensity on the surface of leaves, because of which the rate of photosynthesis in the leaves and physiological growth processes are reduced.