The temperature calculation model of civil Aircraft EE bay under the ventilation failure is established in this paper. The temperature transformation of EE bay after ventilation failure at the ISA+25 益cruise condition is present. For air temperature of EE bay exceeding the limit, three proposals of design or operation are provided as follow: shut off the avionics that have no impact on the flight safety, make use of the pressure difference to extract the hot air overboard providing backup ventilation, or reduce the conduction thermal resistance of the insulation of EE bay.