New trends of atmospheric greenhouse gases in Beijing are reported. A method named decomposition of time series is used to analyze the seasonal variations of three main greenhouse gases in Beijing. The results show that the annual variations of atmospheric methane are ranged from -49.2×    10^-9 to 55.7×10^-9(V/V) and from -26.4×10^-6 to 34.0×10^-6 (V/V) for carbon dioxide. According to our analyses, there are no seasonal variations for nitrous oxide.