Based on the eddy covariance system and LI-8150 automatic soil respiration observation system, this present study investigated the characteristics of net ecosystem CO₂ exchange (NEE), the contribution of soil respiration (R_s) to ecosystem respiration (R_eco), and the gross primary productivity (GPP) in Horqin sandy grassland of China. The results showed that the average monthly diurnal variations of NEE changed apparently with a single peak curve; the highest absorption rate (-5.62 μmol·m^-2·s^-1) and the highest release rate (3.14 μmol·m^-2·s^-1) were observed in July. The sandy grassland ecosystem was a carbon sink, with a sequestration amount of 25.85 g C·m^-2 during the growing season. The contribution of R_s to R_eco accounted for 78.39%; the GPP was 275.51 g C·m^-2 and the contribution of R_eco to GPP accounted for 90.62%.