Abstract: The influence of raw material form upon the physical mechanic properties of the composite panels were studied and the reasons were analyzed by composing two technological types of cotton stalk as raw material (cotton stalk shavings and cotton stalk fibers) with different sized plastic particles to prepare cotton stalkplastic composite panels. The results showed that the comprehensive physical mechanic properties of the composite panels that were prepared by 2 mm plastic particles and cotton stalk were generally superior to those prepared by 5 mm plastic particles and cotton stalk. The comprehensive physical and mechanic properties of the composite panels that were prepared by cotton stalk shavings and plastic particles were generally superior to those prepared by cotton stalk fibers and plastic particles. The physical and mechanic properties of the composite panels prepared with ideal raw material types could meet the demand for making intensified structure flakeboard, which can be used under moist environment.