Asymbiotic nitrogen fixation (ANF) serves as a crucial pathway for nitrogen input in terrestrial ecosystems, holding particular significance for the growth of artificial vegetation in arid and semi-arid regions. However, the characteristics of soil ANF rates and their regulatory factors in artificial forests within the Loess-Hilly Region remain poorly understood. This study targeted Robinia pseudoacacia plantations-the dominant vegetation type in this region-with different stand ages (0, 12, 22, and 33 years). By combining field sampling with laboratory incubation, soil ANF rates were assessed using the acetylene reduction assay to investigate their variation patterns with stand age and soil depth, along with the influencing factors. Our findings revealed that: (1) The soil ANF rate in the Robinia pseudoacacia plantations ranged from (1.97±0.07) to (2.38±0.05) kg N hm^-2 a^-1. It initially increased, peaked, and subsequently declined with increasing stand age, while showing a significant increase with greater soil depth (P<0.05). (2) Soil carbon and nitrogen content, microbial biomass, and extracellular enzyme activities associated with nutrient transformation all increased with growing duration but decreased with soil depth (P<0.05). (3) The altered soil physicochemical properties associated with stand aging modulated soil ANF rates primarily by regulating microbial biomass and extracellular enzyme activities, with soil moisture, available phosphorus, microbial biomass nitrogen, and nitrogen-acquiring enzyme activities identified as key drivers. These results contribute to a more accurate assessment of nitrogen cycling processes in the Loess-Hilly Region and similar arid-semi-arid ecosystems, and provide a scientific basis for sustainable management practices in artificial vegetation systems.