Abstract: In response to the military requirements for missile defense against subsonic cruise missiles, the tail nozzle of turbofan engines equipped on low-speed missiles was taken as the study focuses. Analyzing the processes parameters at various sections of the tail nozzle based on aerodynamics and aircraft engine principles, a mathematical model was proposed to describe the thrust loss due to airflow leakage of typical damaged turbofan engine nozzles during mission. Taking F107-WR-400 series turbofan engine installed in the American BGM-109C Tomahawk cruise missile as the example, the proposed model was applied to calculate the thrust loss of aeroengine under various damage conditions of its tail nozzle. The calculation results show that penetration injuries at different locations can cause varying degrees of thrust loss to the engine, the relationship between the size of damage hole and the reduction of engine thrust is nonlinear, the extent of engine thrust loss under same damage conditions also depends on its working status.