Wood-plastic composites (WPC) are mainly made of plastic and waste wood, rice husk, crops straw or other vegetable fibers, and the products are extensively used in packaging, gardens, transportation, construction, upholsteries, furniture manufacturing, car interior decoration, etc. However, it is not easy to produce WPC product with high-performance and lower production cost, because of the poor interfacial compatibility between the strongly polar lignocellulosic flour and the common non-polar plastic matrixes (PE, PP, PS, PVC, etc.), and the strong self-interaction of the lignocellulosic flour, which cause poor dispersion and mechanical properties. Generally, the compatibility and mechanical properties of WPC could be improved to a certain extent by surface esterification, etherification, graft copolymer or coupling agent pretreatment of the filler. However, these pretreatment processes are complex, not environmentally friendly and the effects are not obvious, so, it could be another effective method to develop WPC with good performance from post-processing. In the present work, crop straw flour/polyethylene (LDPE/CSF) composites without adding coupling agent and compatibilizer were prepared by direct melt blending, and the effect of electron beam irradiation on the structure and properties of LDPE/CSF composites were studied. The results showed that the mechanical properties and water absorption of the LDPE/CSF composites can be improved significantly through the electron beam irradiation, and the interface compatibility was also improved because of the formation of stable cross-linked network structure between LDPE and CSF, on the other hand, due to the increase of crystal defects in PE irradiated by electron beam irradiation, the melting temperature of LDPE/CSF composites decreased. Radiation processing is a good and new technology to prepare wood-plastic composites with excellent comprehensive properties, and with a wide range of application.