Abstract: WF/HDPE composites were prepared from wheat straw fiber (WF) and high density polyethylene (HDPE) by mixing and injection moulding. The effects of xylanase, laccase, lipase, xylanase and lipase on the mechanical properties, thermal stability and water absorption of WF/HDPE composites were investigated. The changes of chemical functional groups of WF before and after enzyme treatment were analyzed by FTIR. The surface morphologies of WF and the tensile fracture surface of WF/HDPE composites before and after enzymatic treatment were observed by SEM. The results show that WF/HDPE composites treated with xylanase and lipase have the lowest water absorption and the best mechanical properties. The tensile strength, flexural strength and flexural modulus of WF/HDPE composites reach 23.4 MPa, 34.0 MPa and 1 944.6 MPa, respectively. TG results show that the thermal decomposition process of WF/HDPE is divided into two parts: WF decomposition process and HDPE decomposition process, and the thermal stability of WF/HDPE composites can be effectively improved by enzyme. After treatment, the hydroxyl vibration peak of WF decreases, and some small peaks appeare in the spectrum at 1 706-1 290 cm⁻¹, and the vibration peak of SiO₂ becomes gentle. SEM shows that the surface of WF becomes rough after enzyme treatment, and WF and HDPE are closely bound, among which the interface bonding performance of WF and HDPE treated by xylanase and lipase is the best.