Abstract: Wood plastic composites were prepared by one-step extrusion of rice hull flour and polyethylene. In the composite silane was used as coupling agent. Influences of different weigh ratios of rice hull and silane on mechanical properties of wood plastic composites were investigated. The test results were as follows: the weigh ratio of rice hull flour to silane coupling agent influenced evidently the interfacial compatibility; impact strength, flexual strength, tensile strength of the composite decreased significantly with the increas of ratio of rice hull flour. So adding optimal ratio of coupling agent could improve the interfacial compatibility and the dispersion of the rice hull in the composites, consequently, the mechanical properties were improved.