Abstract: In order to clarify the temporal and spatial patterns of carbon source and carbon sequestration of forest ecosystem, and to collect the relevant data for forecasting of global climate change, the CO2 flux of northern subtropical secondary oak forest ecosystem was observed by eddy covariance technique, the carbon flux data of the forest ecosystem from December 2007 to November 2008 were obtained by longterm observations. The analyses of response relationship of the carbon flux value (respiration) observed during the whole day in nongrowing season (December-February) and at night of growing season (March-November) to the air and soil temperature showed that there was a significant Van’t Hoff index relationship between the respiration intensity and the air and soil temperature. The respiration observed in nongrowing season fitted the best with air temperature, whereas the respiration observed at night of growing season fitted the best with soil temperature.