Abstract: A controlled study of irrigation and nitrogen (N) supply was conducted in the Hexi oasis to investigate the effects of different irrigation and N supply levels on soil organic carbon(OC), soil total nitrogen(TN), soil carbon and nitrogen ratio (OC/TN) of spring wheat on no-tillage farmland with standing stubble. With an increase in N supply rate, TN and OC contents considerably increased in soils. However, when N supply rates were higher than 140 kg N/ha, TN did not continuously increase with the increase in N supply rate, and OC even showed a decreasing trend. Irrespective of nitrogen levels, with an increase in irrigation level, TN and OC contents initially increased but then decreased in soils. An appropriate amount of irrigation (20% water-saving irrigation) promoted the mineralization rate of soil nitrogen and carbon, thus increasing the TN and OC contents. However, a smaller amount of, or excessive, irrigation reduced soil nitrogen and carbon mineralization rates, and increase soil nitrogen and carbon losses. The highest TN (0.9 g/kg) and OC (14.22 g/kg) were measured under 20% water-saving irrigation. When the N supply rate was 221 kg N/ha, the grain yield reached a maximum (6 365 kg/ha) irrespective of the irrigation levels but the grain yield of spring wheat increased with an increase in irrigation level.