Seasonal variations of soil respiration in two forest types, Sweetgum（Liquidambar formosana) and Camphortree (Cinnamomum camphora) plantations, were measured in Tianjiling National Forestry Park of Changsha, Hunan, China. CO2 effluxes rate was monitored using an infrared gas exchange analyzer (LI-COR-6400-09) from January to December 2007, and the controlling factors, such as soil temperature and moisture were also recorded in the two forests. The results showed that the two plantations had significant different patterns in seasonal soil respiration processes. The two forests exhibited irregular fluctuated curves during the study period with mean rates of soil respiration were 1.501 μmol·m-2·s-1 and 2.800 μmol·m-2·s-1 in Sweetgum and Camphortree stands, respectively. Significant relationships were found between soil respiration rate and soil temperature at 5 cm soil depth in both plantations, which could be best described by exponential equations. However, not significant relationships were found between soil respiration and soil moisture at 5 cm depth. Soil temperature and moisture could explain changes in soil respiration of 92.7%, 77.4% and 10.6%, 18.0%, in the Sweetgum and Camphortree plantations, respectively. The relationship between both soil respiration rate (y) and the two variables of soil temperature (t) and soil moisture (w) at 5 cm soil depth could be described by the following multiple regression equation: y=0.4728e0.122tw0.002(R2=0.945, P<00001),y=0.061e0.235tw0.086(R2=0.885, P<0.001). The multiple equations had much more predicative power than those using only temperature or moisture as a single independent variable. The Q10 values in Sweetgum and Camphortree forests were 2.62 and 3.26, respectively, and tended to decrease when soil temperature increased from lower to higher scales. The seasonal patterns of soil respiration in these two forests were not only determined by soil temperature and soil moisture, but also by the fine root mass and litter production as well.