The ventilation and cooling function of civil aircraft electronic equipment cabin (EE cabin) is the basic function to ensure the safety and normal operation of electronic equipment in cabin. With the continuous improvement of avionics system integration of civil aircraft, more and more system electronic equipment is placed in EE cabin, and the ventilation and cooling function are becoming more and more important. If the ventilation and cooling function fail, how to determine the working condition of the equipment in the electronic equipment cabin, how to determine the impact of the failed equipment on the aircraft, and how to determine the impact level of the failure mode, these problems need to be solved urgently. Based on the principles of determining the failure scene, judging the direct impact, analyzing the indirect impact and analyzing the comprehensive impact of the whole machine, this paper studies the impact rating problem of EE bay ventilation and cooling function failure based on Cascading Effects Analysis Method. By analyzing the architecture and function of EE bay ventilation and cooling system, the failure mechanism of ventilation and cooling function was determined, and the failure scene of ventilation and cooling was defined. Using Cascading Effects Analysis Method, the influence of ventilation cooling failure on the whole machine system was analyzed, which was suitable for the comprehensive safety assessment of ventilation cooling failure, providing technical support for rating the influence of the ventilation and cooling function.