Wave-absorbing composite materials are fabricated with four-needle zinc oxide and carbon black as the absorbent， and silicone resin as the binder. The influence of the content of the absorbent and the thickness of the composite material on the absorbing performance is studied.At the same time， scanning electron microscope， vector network analyzer and other instruments are used to characterize the microscopic morphology and electromagnetic properties of composite absorbing material samples with different mass fractions. The results show that within a certain range， the thickness of the sample， the content of carbon black and the content of tetrapod zinc oxide increase， which will improve the absorbing performance of the sample.When the thickness of the sample is 2 mm and the mass fractions of carbon powder and tetrapod zinc oxide are 8% and 10%， respectively， the minimum reflection loss value of the composite absorbing material can reach-14.68 dB， which is in line with the current light and thin broadband absorbing material development trend. Therefore， the composite material has the advantages of low absorbent content， lightness and thinness， and high elasticity， and has potential application prospects in the field of electromagnetic shielding.