Modification of linear low density polyethlene(LLDPE ) with maleic anhydride(MA)was studied and suitable conditions for LLDPE-MA copolymer preparation in the manufacture ofwood fiber-plastic composites were found.The test data of infrared spectra(IR)and graft-rate de-termination showed the existence of polar groups in the non-polar LLDPE-MA molecule. The results also showed the formation of LLDPE-MA copolymer can be obtained by free group initiationand the extent of reaction of MA to LLDPE can be improved by changing process conditions. Thecopolymer obtained in this study would be very useful for making wood fiber-plastic composite.