Petrochemical-based foam materials are extensively used in insulation and energy storage fields. However, their non-degradability and high flammability have caused great pressure on energy, environment and human life and property safety. It is urgent to carry out research on biodegradable and fire safety alternative biomaterials. Herein, inspired by the natural hollow insulation animal hair, the 3D network structure of tubular aerogel was constructed by using the hollow kapok fibers (KF), the binder polyvinyl alcohol (PVA) and the flame retardant crosslinker biguanide phosphonate (BGP). The multifunctional tubular aerogel integrating thermal insulation, high strength and fire safety was successfully prepared by freeze-forming and freeze-drying. Due to the intermolecular hydrogen bonding and the high viscosity of binder, KF maintained a high filling, full component and high value utilization. Compared to pure KF, the thermal conductivity of KF-PVA-BGP aerogel was reduced to 0.0531 W m−1K−1 and its compressive strength was improved to 1.64 MPa. Meanwhile, the incorporation of flame retardant cross-linker BGP promoted the degradation and charring of KF-PVA aerogel and released lots of inert gases during decomposition process, which effectively exerted the flame retardant effect in condensed and gas phases. Besides, compared with commercial PS insulation boards, KF-PVA-BGP composites are recyclable, sustainable and biodegradable in addition to their excellent thermal insulation and fire safety performance. This KF-PVA-BGP aerogel showed good application prospects for replacing traditional petrochemical-based materials in thermal insulation, energy storage and new energy fields.