Abstract: In order to improve the microwave absorbing properties of single magnetic absorbing material, polylactic acid (PLA) was used as the matrix material, and the magnetic material carbonyl iron powder (CIP) as well as reduced graphene oxide (RGO) were compounded to prepare RGO and CIP/PLA composites. The structure and morphology of the composites were characterized by TG, XRD and other testing methods. Meanwhile, the electromagnetic parameters of the composites were measured by vector network analyzer, and the microwave absorbing properties of different thickness were calculated. The influence of RGO addition on the microwave absorbing properties of RGO and CIP/PLA composites was studied. The results show that when the graphene content is 4wt% and the carbonyl iron powder content is 20wt%, the RGO-CIP/PLA composite has the best absorbing performance. When the absorption thickness is 3 mm, the minimum R_L value of −27.25 dB is reached, and at the same time its absorption bandwidth is 2.922 GHz (7.227-10.149 GHz). At the same time, as its absorption thickness increases, the effective absorption bandwidth (R_L<−10 dB) can move to a lower frequency band.