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To further explore the internal mechanism of organic and inorganic fertilizer application on the fertilizer reduction and efficiency of dryland winter wheat, a fissure zone design was set up according to a 7-year long-term positioning experiment. Five nitrogen levels（0, 75, 150, 225, 300 kg·hm-2 ）were set as the main treatments; a mixed and unapplied organic fertilizer（dosage of 30 t·hm-2 ）was used as a side treatment. The single fertilizer treatment was labeled N0, N75, N150, N225, N300, and the combined organic fertilizer treatment was labeled MN0, MN75, MN150, MN225, MN300. The underground（0~20 cm root system）and aboveground parts of the plant were collected during the tillering, jointing, flowering, filling, and mature stages, and the grain yield and its constituent factors, nitrogen uptake, and utilization were studied. The results showed that, with an increase in the nitrogen application rate, the number of effective panicles and grains per panicle increased first and then decreased, while the 1 000-grain weight decreased gradually. The effective number of panicles in the combined organic fertilizer treatment increased by 7.1% compared with the single application of chemical fertilizer. The MN150 treatment had the highest grain yield, which reached 6 311 kg·hm-2 . The absorption of nitrogen under the single fertilizer treatment was mainly through pre-anthesis nitrogen transport, while pre-anthesis nitrogen transport and post-anthesis nitrogen absorption played equally important roles in the accumulation of nitrogen under the combined fertilizer treatment. Compared with the single application of chemical fertilizer, the combined application of organic and inorganic fertilizers increased pre-anthesis nitrogen transshipment, and post-anthesis nitrogen accumulation, by 9.8% and 33.1%, respectively. Pre-anthesis nitrogen transport mainly occurred in the stems, and nitrogen accumulation reached the highest under the MN150 treatment. Nitrogen use efficiency and agricultural efficiency were significantly increased by organic fertilizer application. A decrease in the nitrogen application rate increased the nitrogen use efficiency, agricultural efficiency, and nitrogen harvest index. Nitrate reductase activity in leaves was significantly increased by nitrogen application, and the highest value was reached under the N225 and MN150 treatments. Nitrate reductase activity increased by 25.94%, 12.88%, 9.90%, and 12.35% during the tiller, jointing, flowering, and filling stages, respectively, under organic and inorganic fertilizer application. In summary, the combined application of organic and inorganic fertilizers at a nitrogen application rate of 150 kg · hm-2 could not only promote the absorption and utilization of nitrogen in winter wheat plants, but also ensured a stable and high yield of winter wheat in a dryland in northwest China. [ABSTRACT FROM AUTHOR]