Soil respiration in forest ecosystems play an important role in global carbon cycle. This study was carried out to determine the annual variation of soil $CO_2$ efflux for 4 years in a broadleaved deciduous forest of the Geumsan (Mt.) Long-Term Ecological Research (GLTER) site in Southern Korea. The soil $CO_2$ efflux in the GLTER site showed annual variations with the fluctuations of annual mean soil temperature, but not with those of soil water content. The annual mean soil $CO_2$ efflux except for winter season was 0.32 g $CO_2;m^{-2}h^{-1}$ for 2008, 0.40 g $CO_2;m^{-2}h^{-1}$ for 2009, 0.41 g $CO_2;m^{-2}h^{-1}$ for 2007, and 0.54 g $CO_2;m^{-2}h^{-1}$ for 2010. The lowest soil $CO_2$ effluxin 2008 was associated with the lowest soil temperature ($2.0^{circ}C$) in comparison with those of other years ($13.0-13.5^{circ}C$). The exponential relationships between monthly soil $CO_2$ efflux and the corresponding soil temperature at the soil depth of 20 cm were significant ($R^2$ = 0.31-0.75, P < 0.05). The results indicate that the annual variation of soil $CO_2$ efflux was attributed to the variations of soil temperature rather than soil water content in the GLTER site.