A pot experiment was conducted to investigate the interactive effect of split application of nitrogen and CO₂ elevation on photosynthesis,dry matter and nitrogen accumulation at heading and middle grain filling stage,and grain yield of winter wheat with open top chambers (OTCs) of wheat variety ‘Xiaoyan 22’.The results showed that CO₂ enrichment had no or negative effect on SPAD value,soluble protein content and photosynthetic ability of flag leaf,dry matter and nitrogen accumulation of shoot after anthesis,and grain yield under no nitrogen application,but under nitrogen addiction (300 mg/kg soil),the indexes increased to some extent,and its effects were mostly significant at 0.05 probability level.Compared with allbased application of nitrogen,CO₂ elevation could increase photosynthetic ability at grainfilling stage,dry matter and nitrogen accumulation of shoot after anthesis,and grain yield under nitrogen split application,especially under nitrogen application with the ratio of 5∶3∶2 at before sowing,regreening and booting stages.It was suggested that CO₂ elevation would preferably increase grain yield of winter wheat under proper split application of nitrogen.