Abstract: An introduction is given to the observation of the land-air interaction over grass in Guangzhou Panyu area in 2004. The observational study shows that although the new type three dimensional sonic anemometer has a rain guard net, the error resulted from the effect of raindrop on observation is obvious especially for the u and w direction. The correlation coefficient between and z/L is low under the rain weather condition, the turbulence intensity and stability has no 1/3 order relationship. The sensible heat flux and latent heat flux calculated by using eddy correlation method are close to those by Bowen ratio energy balance method, the correlation coefficients of sensible heat flux and latent heat flux calculated by the two methods reach 0.8699 and 0.8633 respectively, the errors mainly happen at the period when the surface stability obviously change, namely at noon with maximum of heat flux and at evening or night with minimum of heat flux respectively. The sensible heat flux and latent heat flux calculated by Bowen ratio energy balance method have the relative large positive and negative peaks. The sum of sensible heat flux and latent heat flux (Q_h+Q_e) calculated by eddy correlation method is generally on the side of small, which is not balanced by the available energy (R_n-Q_g) under most circumstances, showing there are some limitations in the surface energy balance equation by neglecting the term of heat storage. The sensible heat flux and latent heat flux have the similar diurnal characters as the solar radiation, the sensible heat flux is larger than latent heat flux in Summer, but the reverse in autumn. CO₂ experiences a diminishing process from May to August, then follow a rising process to a maximum concentration in December, mostly CO₂ concentrations stand at the level of 350×10^-6~400×10^-6.