The effect of the arrangement of thermoelectric cooler （TEC） on the natural convection characteristics of air in the cooling chamber of airborne avionics is studied by experimental research and numerical simulation. The results show that when the air is cooled， its temperature decreases while its density increases， and it begins to sink at a slow speed. Its motion form gradually transitions from deformation to rotation. It is more beneficial to the development of flow field to arrange all the TECs at the top of the chamber. However， when the air sinks to the bottom of the cooling chamber， it is easy to produce oscillation solutions， fork flow and secondary flow， and the flow enters the chaotic state. Through comparative analysis of six design cases， the best arrangement of TEC in the cooling chamber of the airborne avionics with the minimum temperature inhomogeneity coefficient and the lowest average air temperature is given.