Abstract: In order to improve the electrical and mechanical properties of carbon fiber/epoxy (CF/EP) composite, the 12K CF was prepared into CF/EP prepreg using the integrated process of carbon fiber spreading and infiltration. The thickness of CF/EP prepreg was 0.02 mm, 0.03 mm, 0.08 mm and 0.10 mm, respectively. Then CF/EP composite unidirectional laminate was fabricated by the molding process. The influence of the microstructure structure on the resistivity of CF/EP composite laminate, the resistivity of the CF/EP composite laminate as a function of temperature and the response of the laminate resistivity under tensile load were analyzed and tested. The results show that the proportion of the resin-rich pocket with larger area in the CF/EP composite unidirectional laminate is reduced as the prepreg thickness is reduced from 0.10 mm to 0.02 mm, and the resistivity of the CF/EP composite along the thickness direction decreases from 151.3 Ω·cm to 32.1 Ω·cm. This improves the electrical conductivity of CF/EP composite by about 5 times. As the temperature increases, the resistivity of the CF/EP composite laminate decreases gradually, and the rate of resistivity declination of the thick prepreg laminate in the thickness direction is larger than that of the thin prepreg laminate. The resistivity of the CF/EP composite laminate made of thin prepreg under loading has high stability, indicating that the thin layer of prepreg helps to improve the electrical properties of CF/EP composite and the ability of load bearing, thus obtaining higher mechanical properties and electrical properties. The experimental results provide the basis for the structure-functional integration design of the CF/EP composite.