In order to commit to the core concept of energy saving and emission reduction, the preparation of absorbing materials with sustainable development, light weight, strong absorption and wide absorption bandwidth has become an urgent problem that should be solved. As a natural product from nature, ubiquitous bamboo is combined with metal-organic framework on its surface through a simple chemical activation method is demostrated to be an effective method to prepare a composite absorbing material with amazing electromagnetic wave absorption. The prepared bamboo fiber/CoNi alloy (CN-ABF) reaches a minimum reflection loss of −75.19 dB at 11.12 GHz when the thickness is 2.66 mm, and the corresponding bandwidth is 4.56 GHz. The prepared CN-ABF greatly enhances the multi-polarity, dielectric loss, magnetic loss and impedance matching. Sustainable absorbing materials prepared by using biomass as a dielectric carbon-based recombined magnetic metal provide a good research strategy for improving the absorbing performance of materials.