Abstract: The coated bamboo fibres (PUBF) were obtained by using high-reactivity polyurethane (PU) coating agent to coat bamboo fibres (BF), and the mass fraction of isocyanate group (—NCO) in PU coating agent was 14.5wt%. The PUBF/PU casting elastomer composites were prepared by in-stiu polymerization. The BF and PUBF were characterized by FTIR, SEM, XRD and contact angle testing. The results show that the surface of the BF is successfully coated by a thin layer of PU terminated with reactive amino groups (—NH₂), which improves the interface compatibility and interfacial bonding between the BF and the casting PU. When the mass fraction of PUBF in the composite is 3wt%, the viscosity of the prepolymer at 80℃ is only 2.2 Pa·s, which is close to the viscosity of the pure PU. The tensile and tear strengths of the corresponding PUBF/PU composite are 38.0 MPa and 82.9 kN/m, respectively, improved by 51.6% and 25.6% compared with the pure casting PU. The BF pre-coated by high-reactivity PU coating agent is suitable for preparing the PUBF/PU composite.