用超声波协同Fenton氧化的方法对木质素进行改性处理，并制备了高密度聚乙烯/木质素复合材料（HDPE/Lig），分析了改性前后木质素的官能团和分子量变化，并探讨了改性前后木质素含量对复合材料的力学性能、微观结构和流变性能的影响。结果表明：经超声波-Fenton氧化改性后，木质素数均分子量（M _n）从15 034 g/mol下降至6 375 g/mol，甲氧基减少，酚羟基及羧基增加。HDPE/Lig的拉伸强度、冲击强度随木质素含量增加呈现先升高后降低的趋势。改性后，木质素的最佳填充量由10%提高至20%。改性后木质素的分散性和相容性得到提高，材料的微相分离程度降低，物理强制增容效果更好。原木质素导致HDPE黏度增大，木质素经过超声波-Fenton氧化后，可以降低复合材料的黏度、储能模量和损耗模量。

lignin was modified by ultrasonic assisted Fenton oxidation, and high density polyethylene/lignin composites (HDPE/Lig) were prepared. The changes of functional groups and molecular weight of lignin before and after modification were analyzed, and the effects of lignin content before and after modification on mechanical properties, microstructure and rheological properties of the composites were discussed. The results show that the number average molecular weight (M _n) of lignin modified by ultrasonic-Fenton oxidation decreases from 15 034 g/mol to 6 375 g/mol, methoxy group decreases, phenolic hydroxyl group and carboxyl group increase. The tensile strength and impact strength of HDPE/Lig increase first and then decrease with the increase of lignin content. After modification, the optimum filling amount of lignin increases from 10% to 20%. After modification, the dispersity and compatibility of lignin are improved, the degree of microphase separation is reduced, and the physical forced compatibilization effect is better. The viscosity of HDPE is increased by lignin, and the viscosity, storage modulus and loss modulus of HDPE composites are decreased by ultrasonic-Fenton oxidation of lignin.