An engineering model for performance estimation of turbofan engine is developed. Based on the thrust estimation model of turbojet and the efficiency analysis method of turbofan, the model is modified by working cycle analysis for the high bypass ratio turbofan. Thrust and fuel consumption characteristics of turbofan engine could be estimated with the model, and the effect of cycle parameters on engine performance is analyzed. The precision of the model is validated by the experimental data from the references. The model can complete the calculation flow quickly with a small amount of input parameters, which can be used in the aircraft conceptual design to evaluate the effect of turbofan engine parameters on aircraft performance.