In order to analyze the humidity effect on civil turbofan engine performance parameters, the humidity correction module for gas property and component characteristics are led into the engine based on components match method, and the simulation model of ambient humidity effect on civil turbofan engine is established. The humidity effect on engine thrust, spool speed and inlet mass flow are analyzed, and the correction curves are obtained. According to the humidity requirement stipulated in the airworthiness regulation of CCAR25, the humidity effect on 6 key operating conditions in the flight envelope is simulated. Results show that the engine will be affected most on the hot day takeoff, and the thrust will be decreased by 0.56 percent. In order to recuperate the thrust loss, the fan relative correct speed should be raised by 0.23 percent. The simulation results are compared with the humidity correction curves provided by the reference, and the same trend and similar order of magnitude verify the reliability of the simulation model.