Abstract: It mainly explored the hybrid model and mechanism of two kinds of hybrid composite materials reinforced with different diameter fibers which were composed of small-diameter fibers nested between large-diameter fibers in a matrix. T300 carbon fiber(CF), SiC fiber and boron fiber(BF) were used. Three types of single fiber composites and hybrid composites with carbon fibers as small-diameter fibers, SiC and boron fibers as large-diameter fibers in epoxy resin matrix were constructed. Triangle and quadrilateral formations were proposed as the hybrid models. The effects of processing on hybrid arrangement and fiber volume fraction were analyzed.