The unstable Zn interface, stemming from dendritic and parasitic side reactions, has posed significant challenges to the large-scale implementation of aqueous zinc ion batteries (ZIBs). Herein, a biobased multifunctional cellulose levulinate ester additive, featured by an acetyl propyl ketone moiety, was proposed to regulate the Zn anode/electrolyte interface chemistry. The well-designed cellulose levulinate ester exhibits strong adsorption capacity, fascinating in-situ protective layer, and exposed both hydrogen-bonding acceptor and donor due to the keto-enol tautomerism. The in-situ constructed organic-inorganic bilayer solid-electrolyte interphase enriched with ZnCO3-ZnF2-ZnS component effectively inhibits Zn dendrites, alleviates corrosion, and improves cycle stability. Consequently, the Zn(OTf)2/CLE electrolyte demonstrates highly reversible plating/stripping capability, enabling cycling for more than 2800 h in the shelving-recovery test, affirming their adaptability for long-term aqueous ZIBs. As a conceptual verification, the assembled Zn//MnO2 cells display exceptional cycle stability with a high capacity retention of 78.6% after 3000 cycles. The in-situ construction of a protective layer on the Zn anode using a biobased multifunctional cellulose levulinate ester additive offers an effective strategy for achieving high-performance Zn metal anodes in aqueous ZIBs.