Natural plant fiber-reinforced biopolymer composites are attractive for their renewable, degradable, and low-carbon, compare to petroleum-based composites. However, the poor interfacial compatibility of bio-composites between fibers and matrix has long been recognized as the biggest challenge. Surface modification of natural fibers or polymers is considered the most common method to address this issue, which is always high energy consumption, and high pollution. Hence, we focus on cleaner and more economical solutions to overcome this difficulty. We pioneered the introduction of a novelty coordination-driven interface system into fibers-filled bio-composites. The chief object of this study is to investigate the iron ions (Fe3+) coordination drives the tannic acid (TA) interface and how to enhance composite interfacial compatibility and promote bio-composite properties. The way of interface formation is cleaner, simpler, more energy efficient, and effective, and the performance of biocomposites has been enhanced, including mechanical (tensile strength, flexural strength, and impact strength increased by 21.65%, 19.41%, and 52.24% respectively. The flexural strength and modulus even reached 59.65 MPa and 6.61 GPa), thermal (Tonset and Tmax increased from 267.39 °C, 377.76 °C–290.13 °C, 389.24 °C, respectively), crystallization (Crystallinity increased by 52.35%) and hydrophobic performance. To summarize, the coordination-driven interfacial system proposes a simple and workable structural model in the field of natural plant fiber-reinforced biopolymer composites interface.