Abstract: By using static chambergas chromatograph technique, an in situ measurement was conducted on the soil CH₄,CO₂, and N₂O fluxes in a coldtemperate Larix gmelinii forest in Inner Mongolia from June to September 2007, aimed to understand the diurnal and seasonal variations of soil greenhouse gasses fluxes and their relations with the associated environmental factors in L. gmelinii forests in coldtemperate zone. In growth season, the soil in the L. gmelinii forest was the sink of atmospheric CH₄, with the flux ranged from 22.3 to 107.8 μg CH₄C·m^-2·h^-1. The mean monthly uptake of CH₄ in June, July, August, and September was 34.0±7.1, 71.4±9.4, 86.3±7.9, and 40.7±6.2 μg·m^-2·h^-1, respectively. The mean diurnal flux of soil CH₄ from June to September showed the same variation trend, i.e., peaked at 10:00 am. The diurnal variation of soil CO₂ flux showed an obvious doublepeak, and the mean monthly CO₂ flux was in the order of July>August>June> September. Soil N₂O flux varied dramatically from -9.1 to 31.7 μg·m^-2·h^-1. Soil temperature and humidity were the main factors affecting the CH₄ and CO₂ fluxes, and soil temperature mainly affected the N₂O flux. In the L. gmelinii forest, the CH₄, CO₂, and N₂O fluxes measured at 10:00 am could represent the diurnal CH₄, CO₂, and N₂O fluxes on the same day.