Abstract: Systematic study has been made on the effect of heat treatment on the mechanical properties of carbon fibre with Ni coating,SiC coatingand SiC-Ni duplex coating.It is shown that tensile strength of the fibre increases with the increasing of thickness of SiC coating.The fracture way of the fibre coated with SiC is pull-out.The strength of SiGcoated fibre does not decrease after heat treatment.The strength of SiC-Ni-coated fibre decreases slowly during heat treatment.The strength of Ni-coated fibre decreases quickly.The reason that the strength of the fibre decreases and fracture mechanism of the coated fibre are analysed.