Abstract: In order to deeply analyze the damage mechanism of carbon fiber reinforced polymer(CFRP) composite with fastener and the influence of specimen size on the damage area of CFRP under lightning environment, the lightning damage experiment and simulation research were carried out on two different sizes of CFRP with fastener. According to the thermo-electric coupling theory, the thermo-electric coupling model of mechanical fastened CFRP was established by ABAQUS, and the temperature field distribution of CFRP under the action of single lightning current A component was obtained. The damage characteristics of CFRP under lightning damage experiment were evaluated using the ultrasonic C-scan. Under this lightning strike condition, the experimental and simulation results show that the lightning current is spreading throughout the thickness of the CFRP specimen through the fastener. The damage area of the CFRP specimen is small when the amplitude of the lightning current is not too large, but the damage area increases sharply and specimen delaminate throughout the thickness with the increase of the current amplitude. The damage stratification, damage morphology and area of CFRP with fastener of different sizes are similar at the similar current, the specimen size variation has little influence on the damage characteristics. The experimental and simulation studies provide a simulated and experimental data support for the structural design of CFRP.