Directional thermal radiation of canopy was studied and the related model was set up.According to the mechanism of radiative transfer,3D canopy scenes were established and the scenes were discretized by differential cells.According to the observed geometric parameters,the radiative transfer of scatter and emission for every internal cell and among cells was calculated.Finally,the directional thermal radiation of canopy could be retrieved from the integral calculation of all differential bodies in the hemisphere under the fixed observations geometric is performed, the polar map of total canopy directional thermal radiation can be drawn. We use the existing in-situ data to test the simulating results of 3D radiative transfer model,the correlation coefficient are 0.91 and 0.79, the RMSE are 0.4 K and0.6 K. It showed that the model is effective and able to improve the precision of temperature inversion and component temperature inversion.