The recycling of crop straw and waste plastic related to environmental pollution control and improvement.In this paper,we study the effects of different kinds of coupling agents on the mechanical properties and the microstructure change of the composite; MAPP、MAPE and TSZ as the coupling agent to enhance the interfacial adhesion between straw fiber and HDPE. The results indicate that: Coupling agents can modify the Straw/HDPE composites’ combined state of the two phases interfaces. MAPE can improve the mechanical properties of composites better than MAPP. Adding TSZ would suppression the two interfaces combination of HDPE and straw, depress the mechanical properties.DMA shows that adding MAPE in the composites, the storage modulus and glass transition temperature increased, the damping performance decreased. SEM shows that after adding MAPE the combination of composites have significantly improved.