Random chopped short carbon fibers (C-sf)/phenol-formaldehyde resin (PF)/SiC powder mixtures are used as filler for the joining of C-f/SiC composites to obtain SiC interlayer at the joining region. The influences of C-sf on the microstructure and mechanical properties have been investigated. Research shows that the introduction of C-sf can improve the microstructure uniformity of the joint and reduce residual silicon content in the interlayer. The joint achieve a high flexural strength of 232 +/- 33MPa as the carbon fiber content is 30wt.%, which is similar to that of the C-f/SiC composites (220 +/- 21MPa). The decrease in residual silicon content and the formation of nano-sized SiC particles are the main reasons for high joining strength.