In order to elucidate the effects of nitrogen (N) and phosphorus (P) addition on nutrient utilization characteristics of grassland dominant species and explore the changes mechanism of grassland community structure and species diversity in loess hilly-gully region, five typical dominant species of common grassland communities including Bothriochloa ischaemum, Stipa bungeana, Lespedeza davurica, Artemisia sacrorum, and Artemisia scoparia, were selected as research objects. A split-plot N and P addition experiment was conducted, with N addition as the main-plot and P addition as the subplot [main-plot: 0 (N0), 25 (N25), 50 (N50), and 100 (N100) kg N hm^-2 a^-1; subplot: 0 (P0), 20(P20), 40 (P40), and 80 (P80) kg P₂O₅ hm^-2 a^-1]. The leaf N and P ratio, N use efficiency, P use efficiency, N reabsorption efficiency, P reabsorption efficiency, relative biomass and their relations of the five dominant species were investigated. Results showed that the reabsorption efficiency of N and P was positively correlated, and their response to N and P addition amount was coupled in each dominant species. Under different N and P additions, L. davurica had the highest leaf N and P ratio, but possessed the lowest N reabsorption efficiency and P reabsorption efficiency. Under different N and P additions, B. ischaemum and S. bungeana had higher N reabsorption efficiency, P reabsorption efficiency, N use efficiency and P use efficiency than other species. Under P addition alone and combined with N25, the relative biomass of each dominant species was positively correlated with leaf N and P ratio and P use efficiency, while negatively correlated with N use efficiency, N reabsorption efficiency and P reabsorption efficiency. The relative biomass of each dominant species showed positive relationships with N reabsorption efficiency, P reabsorption efficiency, N use efficiency and P use efficiency, while showed negative relationships with N and P ratio under N addition alone or N50 and N100 combined with P addition treatments. Under unfertilized condition, B. ischaemum and S. bungeana had the highest relative biomass. Under low N and high P conditions, L. davurica had the highest relative biomass, while A. sacrorum and A. scoparia had the highest relative biomass under high N and high P conditions. Different dominant species showed different physioecological processes in responses to N and/or P addition, which determined their dominance in the grassland community, and this is the key mechanism for the change of grassland community structure and species diversity after N and P addition.