By using static chamber and gas chromatography methods, this paper studied the effects of clear cutting and selective cutting on the CO2, CH4, and N2O emissions from Larix gmelini-Sphagnum swamp in Lesser Xing' an Mountains. Dramatic changes in the seasonal dynamics of CH4 and N2O emissions were detected in different treatment sites. Control site absorbed CH4 in summer and emitted CH4 in autumn, and absorbed N2O in both summer and autumn; selective cutting site emitted CH4 and N2O mainly in summer; and clear cutting site emitted CH4 in summer and autumn, and absorbed N2O in summer but emitted it in autumn. Cutting pattern had less effects on the seasonal dynamics of CO2 emission. Both on the clear cutting site and on the selective cutting site, the CO2 emission was in order of summer > spring > autumn. Forest cutting altered the source and sink functions of the sites. Control site functioned as a source of CO2 and a weak sink of CH4 or N2O, while forest cutting sites had a decrease of CO2 emission by 25%, and became a weak source of N2O and a weak or strong source of CH4. Compared with that of control site, the Global Warming Potential (GWP) of selective cutting site and clear cutting site was reduced by 24.5% and increased by 3.2%, respectively.