Abstract: Grassland ecosystems are a major component of terrestrial ecosystems in arid and semi-arid regions and play an important role in regional carbon balances. Continuous observation (from 2015 to 2016) of carbon dioxide flux was conducted using the eddy covariance technique in the ‘Horqin Sandy Land’ grassland ecosystem. The study period coincided with the drought in the study area and the annual rainfall during the study was 60% of the historical average. Key results were: 1) The maximum daily absorption rates were -6.68 and -9.58 g·m^-2·d^-1, respectively, in 2015 and 2016, while the release rate was 5.69 and 5.21 g·m^-2·d^-1. 2) The amount of CO₂ absorption was -120.54 and -139.83 g·m^-2 during growing season and the emission was 230.33 and 212.82 g·m^-2 during the non-growing season. 3) The Horqin sandy grassland ecosystem was a carbon source when considered from an annual perspective. The net carbon release in 2015 (109.79 g·m^-2·yr^-1) was slightly greater than that in 2016 (72.99 g·m^-2·yr^-1). 4) There were significant correlations between net ecosystem exchange (NEE) and air temperature, soil temperature, and soil moisture. However, the response of NEE to environmental temperature and humidity was not consistent across the two years.