The exchanges of CO2 and heat between vegetated land surface and the atmosphere are coupled processes through the stomates of plants leaves. A model simulating both the CO2 and heat fluxes between land surface and atmosphere simultaneously could be of more physical and physiological bases. In this paper, a new solution method of a coupled energy and CO2 flux model will be introduced to improve the model stability and computational efficiency. The model is then tested with data from the 1997 Southern Great Plains Experiment (SGP97, http://hydrolab.arsusda.gov /sgp97/). These data include surface temperature, surface soil moisture, land cover and land use maps, meteorological observations of the area over the El Reno, Oklahoma site for the time period from June 18 to July 16, 1997. The model could be driven either by surface temperature or by the surface soil moisture remotely sensed with the Electronically Scanned Thinned Array Radiometer (ESTAR). Model estimates of energy fluxes will be tested against data from Energy Balance Bowen Ratio (EBBR) stations of the Atmospheric Radiation Measurement Program (ARM). CO2 flux estimation from the model will be compared with the data from the Twin Otter aircraft data of SGP97. Feasibility for using the model to map the CO2 and energy fluxes of the whole SGP97 region will be discussed.