Abstract: Large amounts of recycled polyvinyl butyral (RPVB) are produced in China every year. Making full use of RPVB not only reduces the cost, but also plays an important role in energy saving, environmental protection and low carbon. In the present work, the natural sisal fibers were dewaxed and treated with alkaline, then microfibrillated with mechanical treatment, and the obtained sisal microfibrils (SMF) were finally made into a mat form. RPVB was crosslinked by glutaraldehyde (GTA) and sodium borate (SB). The SMF/crosslinked RPVB composites were prepared by solvent impregnation technique. The structure and properties of the composites were analyzed by using SEM, FTIR, TG and mechanical tests. The results show that alkaline-mechanical treatment can successfully separate natural sisal fibers with the diameter of 150-200 μm into microfibrils with the diameter of 5-10 μm and aspect ratio of length to diameter higher than 100. GTA and SB could successfully crosslink the RPVB, and the elongation at break of obtained composite films increases considerably. The interfacial adhesion of RPVB and SMF is good, however, the uniformity of the composites is not good enough, due to the fact that only part of the RPVB penetrates into the interior of sisal microfibril mat. The TG analysis shows that the thermal stability of SMF/RPVB composites is intermediate between RPVB and SMF.