［Objective］The green and environmentally friendly fully bio-based flame-retardantimpregnating solution for lyocell fabrics with ultra-efficient flame-retardant and excellent wearingperformance were prepared in the water solvent.［Methods］Phytic acid（PA）and copper gluconate（CG）were used to synthesize the flame-retardant impregnating solution（PC），then the flame-retardant lyocell fabrics（Lyocell/PC） were prepared through impregnation，rolling and baking processes. Characterization was performed using X-ray photoelectron spectroscopy（XPS）and scanning electron microscopy energy dispersive spectroscopy（SEM-EDS）.［Results］The PC was successfully preparedand applied to the surface on the lyocell fabrics. When the loading of PC reached 3. 6%，the limiting oxygen index（LOI）of Lyocell/PC increased to 29. 3%. Besides，it passed the vertical burning test（VBT）， and the heat release was significantly suppressed. The flame-retardant mechanism indicatsthat PC could decompose in advance to form dense carbon layers to protect lyocell fabrics duringcombustion. Meanwhile，it produced a large amount of non-combustible gases to dilute the concentration of combustible gases in the air，achieving a good flame-retardant effect. In addition，compared with pure lyocell fabrics，Lyocell/PC fabrics had no change in strength，moisture regain，air permeability，and hand feel.［Conclusion］The fully bio-based flame-retardant impregnating solutionnot only could be prepared using a green and environmentally friendly method，but it could also endow the lyocell fabrics with excellent fire safety and wearing performance.