To overcome the long processing time of isothermal chemical vapour infiltration, microwaves are introduced into chemical vapour infiltration developing a method named microwave pyrolysis chemical vapour infiltration for the fabrication of carbon/carbon composites. The process was performed at deposition temperature of 1100°C, with a residence time of 0·15 s under different gas partial pressures, using nitrogen gas as diluent gas and methane as carbon source gas. The densification rate of the preforms, the bulk density of the samples and the uniformity of density were investigated. The deposition process of the microwave pyrolysis chemical vapour infiltration and the microstructure of as prepared samples were analysed. Results show that carbon/carbon composites with bulk density of 1·70 g cm–3 can be prepared with the microwave pyrolysis chemical vapour infiltration process in 90 h, the preforms can be densified from the inside out, and the densities of composites first increase and then decrease with increasing methane partial pressure. High textured pyrocarbon can be prepared by the microwave pyrolysis chemical vapour infiltration, and optical anisotropy gradient is increased gradually with increasing methane concentration. Furthermore, this research provides a novel method or good idea for the low cost fabrication of the carbon matrix composites, such as C/C, SiC/C and SiC/C/C composites.