In order to explore the main influencing factors of femtosecond laser cutting of carbon fiber reinforced resin matrix composites (CFRP), the influence of different energy densities and spot overlap rates on the width of the heat affected zone, surface roughness, and slit taper was investigated using the controlled variable method. Based on the dual temperature equation, the temperature field evolution process of the electron lattice during the interaction between femtosecond laser and carbon fiber was si-mulated using the time difference method. The experimental results show that under the condition of constant pulse frequency, increasing laser power can increase the width of the heat affected zone of the cutting seam, increase the roughness and taper of the cutting seam, and decrease the cutting quality; Under the condition of fixed laser power and a single increase in pulse frequency, the cutting quality decreases but tends to saturate as the pulse frequency increases. The simulation results show that the higher the energy density, the higher the equilibrium temperature of electrons and lattice, the longer it takes to reach thermal equilibrium, and the more obvious the thermal effect. The analysis points out that the overlap rate of light spots and the pulse energy density are two important factors affecting the processing quality. Variations in laser power and pulse frequency can change the pulse energy density and overlap rate of light spots, indirectly affecting the processing quality.