Abstract: With the rapid development of wireless communication technology, the problem of electromagnetic interference is becoming increasingly serious, and the development of high-performance and low-cost microwave absorbing materials has become an urgent need. In this study, CoFe/C composites were successfully prepared by impregnation method with high-temperature calcination process using low-cost waste filter cotton as carbon source. By systematically studying the effects of calcination temperature (600—800 ℃) and impregnation solution concentration (0.1—1.0 mol/L) on the microstructure, electromagnetic parameters, and absorption properties of composites, it was found that a suitable amount of CoFe alloy loading can effectively optimize impedance matching, and the synergistic effect of dielectric loss and magnetic loss enables it to exhibit excellent absorption properties in the 2—18 GHz frequency band. The experimental results show that when the calcination temperature is 700℃ and the impregnation solution concentration is 0.5 mol/L, the CoFe/C composite prepared has a minimum reflection loss (RL_min) of −67.46 dB at a matching thickness of 1.7 mm; When the matching thickness is 1.5 mm, the maximum effective absorption bandwidth (EAB) is 4.44 GHz. This study not only realizes the high-value utilization of waste filter cotton, but also provides new ideas for the development of low-cost and efficient absorbing materials.