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.