To investigate the effect of different CO₂ concentrations and nitrogen application on net CO₂ fluxes in wheat field,an automatic CO₂ concentration control platform consisting of open-top chamber (OTC) was used to simulate an elevated CO₂ concentration environment.Three CO₂ concentration levels were set:CK (ambient atmospheric CO₂ concentration),C₁(CO₂ concentration increased by 120 μmol·mol^-1 compared with CK) and C₂(CO₂ concentration increased by 200 μmol·mol^-1 compared with CK);two nitrogen fertilizer treatments were set at regular nitrogen fertilizer (N₁,25 g·m^-2) and low nitrogen fertilizer (N₂,15 g·m^-2).The net CO₂ fluxes in the wheat field were observed using a static chamber-high precision gas analyzer.The results showed a consistent trend of net CO₂ fluxes in wheat field under all treatments:increased until peaked at the jointing and heading stages,and then decreased.Under the N₁ treatment,the CO₂ accumulation under CK,C₁ and C₂ treatments were-105.8±12.6,-123.1±11.5 and-120.2±4.1 kg·hm^-2,respectively.Under the N₂ treatment,the CO₂ accumulation under CK,C₁ and C₂ treatments were-82.3±9.2,-95.4±7.6 and-96.7±2.8 kg·hm^-2,respectively;the CO₂ accumulation of C₂ treatment at jointing stage was significantly higher than that of CK by 31.8%(P=0.024).Under the C₁ treatment,the CO₂ accumulation of N₁ treatment was significantly higher than that of N₂ treatment by 55.0%(P=0.009) at the jointing stage.Under the C₂ treatment,the CO₂ accumulation of N₁ treatment was significantly higher than that of N₂ treatment by 23.6%(P=0.010) during the whole growth stage.The correlation between net CO₂ fluxes and soil moisture reached significance under all treatments.Under the N₁ treatment,the correlation between net CO₂ fluxes and photosynthetic effective radiation under C₁ and C₂ treatments was significant,and under the N₂ treatment,the correlation between net CO₂ fluxes and photosynthetic effective radiation under CK and C₁ treatment was significant.Under the N₁ treatment,the correlation between net CO₂ fluxes and air temperature was significant only under C₁ treatment.This study showed that the effect of nitrogen application on the net CO₂ fluxes in wheat field was more significant than that of elevated CO₂ concentration at the jointing and heading stages of wheat,and there was no significant interaction between the elevated CO₂ concentration and nitrogen application on the net CO₂ fluxes in wheat field.