Abstract: In order to accurately measure the topography and dimension of the interphase structure in carbon fiber reinforced resin matrix composites, a quantitative, in-situ nanomechanical imaging technique was used to map the dynamic mechanical properties of carbon fiber reinforced thermoset resin matrix composites. This technique for interphase structure testing was analyzed including parameter setting, data processing and its applicability. The results indicate that the nanoscale lateral resolution of the method can resolve the width and topography of the interphase in carbon fiber composites. For the carbon fiber/epoxy resin and carbon fiber/bismaleimide resin systems, the storage modulus presents the gradient change in the interphase region. The average interphase width is about 100 nm obtained by statistical analysis on the storage modulus image, and the morphology of interphase on the cross section is “river-like”, which is similar to the surface topography of carbon fibers.