Populus euphratica is a drought-tolerant species unique to desert region that plays a crucial role in carbon sequestration in desert oases. However, how plant-and microbial-derived C contribute to soil organic carbon (SOC) changes during stand development and the influence of soil environmental factors on these changes remains unclear. Here, biomarkers (amino sugars and lignin phenols) were used to track contributions of plant-and microbial-derived C to SOC at two soil depths (0-20 and 20-40 cm) in P. euphratica desert forests of four stand ages (5, 15, 30 and 105 years). The contribution of microbial-and plant-derived C to SOC increased with stand age in 0-20 cm soil layer. Among these, plant-derived C made a higher contribution to SOC compared to microbial-derived C (2.2-17.8 % and 1.1-13.1 %, respectively), and the contribution of bacterial-derived C to SOC was lower than that of fungal-derived C. Gradual increases in total nitrogen (TN), total phosphorus (TP), and the silt-clay mixture content were observed in the 0-20 cm soil layer with stand age. Stand development enhanced phenol oxidase activity in both two depths. Additionally, the accumulation of plant-derived C was strongly correlated with plant above-ground biomass and soil nutrients (TN and TP), and shifts in microbial-derived C accumulation were induced by the increase in soil silt-clay mixture content during stand development. Our study offers novel insights into SOC accumulation in P. euphratica forests of extreme arid areas, and helps elucidate the distinct mechanisms of plant-and microbial-derived C accumulation in desert soils during forests development.