Abstract: Thermosetting composites have been widely applied in many fields due to their excellent mechanical properties, heat resistance, and chemical resistance. However, the drawbacks including non-renewable raw materials, non-recyclability after service, and non-degradability of fibers and resins largely limit their further application. In this work, two bamboo fibers, i.e., micrometer-scale bamboo powders (BP) and centimeter-scale bamboo fibers (BF) were respectively used as reinforcements for the resin matrix from epoxidized soybean oil (ESO), and meanwhile, a dithiol monomer containing dynamic borate esters was used as a curing agent. The recyclable bamboo fibers reinforced soybean oil-based vitrimer (ESOBV) biocomposites were prepared via a compression molding technique. The tensile properties, dynamic mechanical properties, stress relaxation, interfacial bonding, recyclability, and degradability of the composites were investigated. The results show that the tensile strength and tensile modulus of the composites decreased with the increase of BP content, while increased with the increase of BF content, indicating a significant effect of fiber morphology on the mechanical properties of the composites. Due to the presence of dynamic covalent bonds, the composites showed a stress relaxation behavior at high temperature, and their stress relaxation times increased with the fiber contents. The BP-reinforced composites can be remolded at high temperature, and the remolded composites have 91.0% tensile strength, 96.3% tensile modulus, and 110.7% elongation at break of the original composites. The dynamic borate esters in ESOBV can exchange with glycerol at 100℃ and atmospheric pressure, and thus the matrix can be degraded in glycerol to recover the fibers without any damage in morphology.