Static chamber-gas chromatographic techniques are used for studying the emission of greenhouse gases CO₂,CH₄ andN₂O from a typical Nei Monggol semi-arid grassland.The pattern of diurnal variations of CO₂ emission in different seasons is almost the same,and the total effect of CO₂ exchange with the atmosphere is net release.The key factors that decide the patterns ofN₂O and CH₄ emissions are soil physical properties and soil water content,and temperature determines the intensity of diurnal variations.Because of the relatively fixed diurnal variation pattern of Greenhouse gases emissions from the Nei Monggol Grassland,weekly observed results in the same growth stage can be corrected to get more accurate and representative data.