Abstract: A shear test machine was designed according to the needs of composite pins’ shear tests. An electric universal testing machine was used to test the quasi-static in-plane shear properties of C/C composites, and a drop weight impact testing machine was used to test the dynamic in-plane shear properties of C/C composites. Then the shear failure mode and shear failure mechanism of C/C composite pins were analyzed using the SEM test apparatus. The results show that the shear failure strength of C/C composite pins is sensitive to strain rate, and it increases remarkably with the increasing strain rate. The shear failure mode of C/C composites is sensitive to the strain rate. Under quasi-static loading, the fiber/matrix interface is seriously debonded and the C/C composites show “pseudo-plastic” failure characteristics, while under dynamic loading, almost all the fibers are surrounded by matrix and the composites show “brittle” failure characteristics. The difference of C/C composites’ shear failure modes under different loading rates is related to the strain rate sensitivity of the expansion of internal-cracks.