Graphene oxide (GO) is used as the substrate material and MgCl₂ is used as the catalyst. Under a mixed atmosphere of N₂ and NH₃, GO is converted into reduced graphene oxide (RGO) by chemical vapor deposition. Meanwhile, collapse boron nitride nanotubes (CBNNTs) are grown on its surface to synthesize RGO/CBNNTs composite materials. By controlling the reaction temperature (800, 850, 900 ℃), the generation of by-product MgF₂ can be effectively inhibited and the growth of the inner diameter of CBNNTs tube wall can be controlled, thereby preparing three types of RGO/CBNNTs composite materials. The wave absorption performance of RGO/CBNNTs composite in the 2-18 GHz frequency band is investigated by attaching CBNNTs of different pipe diameters to the surface of RGO. Among them, the absorption performance of RGO/ CBNTS-900 is the best. According to the test data, at 13.36 GHz, the minimum reflection loss (RL_min) of RGO/ CBNTS-900 reaches −49.17 dB, and the matching thickness is only 1.59 mm. All the above parameters are stronger than those of RGO. Due to the high electrical conductivity and large dielectric constant of RGO, it is extremely prone to causing electromagnetic impedance mismatch problems. The introduction of CBNNTs has reduced the ε' of RGO from 7.7 to 5.1, alleviating the problems of high electrical conductivity and large dielectric constant of RGO, and improving the microwave absorption performance. This method provides a new idea for the application of RGO materials in the field of microwave absorption.