Abstract: Wood plastic composites (WPC) were prepared by alkali lignin, eucalyptus powder, high density polyethylene (HDPE) and additives through extrusion granulation and hot compression molding. The effects of alkali lignin content on the properties of WPC were multi-analyzed in the study. The results show that alkali lignin can be used as one of the raw materials to prepare WPC materials, and within a certain range of lignin content, the internal structure of the prepared WPC materials was more compact and uniform. Meanwhile, the addition of alkali lignin can also improve the tensile strength, impact strength and dimensional stability of the composite materials. Furthermore, the decay experiments show that WPC prepared by lignin have preferable decay resistance against decay fungi. Through multi-analysis of experimental results, the optimum formulation is proposed with the addition amount of alkali lignin is 10%–15%.