We propose a thermal bidirectional gap model to describe the thermal directional emission from row crop canopies. An important concept of overlap index is used in this model to express the correlation between the gaps in the Sun and view directions. Detailed directional thermal emissions, row structure, LAI, component temperatures were measured in the experiment taken in Shunyi China, 2001. These data are used to validate our model. As an illustration, we compared our bidirectional gap model with the model that doesn't consider gaps (Kimes model) and the model only consider gaps in view direction. It is found that our model gives out the closest results to the field measurements.