High-power aviation airborne electronic equipment will have the problem of over-temperature. Compared with air cooling, the use of the liquid cooling to cool the device has better heat dissipation effect, so the thermal characteristics of the liquid cooling system need to be simulated and calculated. Taking a certain type of airborne liquid cooling as an example, the theoretical calculation model of heat transfer of the main components (such as liquid storage tank, gear pump, radiator, etc.) was established, and the temperature under -40℃~40℃ was simulated and analyzed. The thermal characteristics of the system, and through the state machine programming to achieve temperature control simulation under over-temperature conditions. The results show that the temperature index of this type of airborne liquid cooling system basically meets the technical index requirements of the cold plate inlet temperature (5℃~30℃) under typical working conditions; The fan speed or the control method of opening the ram air port can obviously improve the problem and the cold plate temperature is basically controlled in the range of 5℃~15℃.