In order to clarify the melting and solidification characteristics of CF/PEEK irradiated by a flat top laser, the mathematical model of the square flat top laser beam and the geometric model of CF/PEEK composites are constructed in this paper. The heating process of the square flat top laser irradiated CF/PEEK and the cooling process after the heating is stopped are calculated and simulated using the COMSOL finite element simulation software. The square flat top laser power density is 5 MW/m, and the power ratio of the flat top area is 94.37%. The surface temperature of CF/PEEK reaches about 370 ℃ after heating for 15 ms. The temperature difference within the irradiation area along the axial direction of carbon fiber is within 0.5 ℃, and the temperature difference at the edge of the irradiation area is about 1 ℃. The temperature curve in the irradiation area along the radial direction of the carbon fiber is wavy, with the temperature difference between the wave crest and the wave trough of 4 ℃, and the temperature difference at the edge of the irradiation area of about 5 ℃. In CF/PEEK solidification process, there will be small molten pool area and large solid-liquid coexistence area.