Abstract: Using CO₂ flux data of winter wheat recorded by eddy covariance system, combined with the meteorological data, we examined the diurnal variations of CO₂ fluxes in four growth stages (tillering stage, overwintering stage, jointing stage and filling stage) of winter wheat in an agroecosystem of the North China Plain from 2013 to 2014. The seasonal variation of net ecosystem exchange and its relationship with meteorological factors were investigated. The results showed that the net ecosystem exchange in the whole growing season was -360.15 g C·m^-2. The gross primary productivity in the whole growing season was 1920.01 g C·m^-2. The winter wheat agroecosystem had strong capacity in carbon sequestration. The CO₂ fluxes showed an obvious diurnal and seasonal variation characteristics in winter wheat agroecosystem. This ecosystem was a carbon source in tillering stage, while it was a carbon sink in overwintering stage, jointing stage and filling stage. The mean value of apparent initial light energy utilization was 0.03 mg CO₂·μmol^-1. The mean value of ecosystem production was 1.53 mg CO₂·m^-2·s^-1 when light was saturated. The monthly average value of ecosystem respiration was 193.92 g C·m^-2·month^-1. The net ecosystem exchange and photosynthetically active radiation had a significant correlation in four growth stages of winter wheat. The correlations between net ecosystem exchange and vapor pressure deficit were significant in all the growth stages. There was a positive correlation between daily total net ecosystem exchange and soil temperature in tillering stage, overwintering stage and filling stage, but a negative correlation between them in jointing stage.