Abstract: The hybrid modified industrial lignin (OMIL-PEI) consisting of industrial lignin oxidatively modified by H₂O₂ (OMIL) and polyethylenimine (PEI) was prepared. Using wood fiber (WF) as the matrix and OMIL-PEI as natural binder, the green OMIL-PEI/WF composites were prepared by the method of high speed mixed-flat of hot pressing. The orthogonal theories were used to analyze the effect of H₂O₂ dosage, oxidative time, mass ratio of OMIL to PEI and OMIL-PEI dosage on the mechanical properties and optimize the process parameters. The structure and property of the composites were analyzed by FTIR, XRD, DMA and SEM. Results show the optimum conditions are as follows: H₂O₂ dosage is 20wt%, oxidative time is 120 min, mass ratio of OMIL to PEI is 7:1 and OMIL-PEI dosage is 20wt%. The mechanical properties of OMIL-PEI/WF composites meet the mechanical property requirements of load bearing medium density fiberboard in dry state according to GB/T 11718-2009. The wood fiber gets a good chemical bond with OMIL-PEI. The crystalline structure of lignocellulose is not changed in OMIL-PEI/WF composites under the optimum conditions. The relative crystallinity increases from 60.24% for pure wood fiber to 72.91% for OMIL-PEI/WF composites. OMIL-PEI improves the dynamic storage modulus of OMIL-PEI/WF composites, but has not much effect on the thermostability of OMIL-PEI/WF composites. OMIL-PEI/WF composites has a good interfacial bondability with uniform mixtures.