Abstract: In this paper, the effects of various wheat straw pretreatment methods (hot-water, acetic acid, sulphite, and xylanase) on the properties of straw fiberboards bonded with UF resin were investigated. The results showed that pretreatment with xylanase was the best in terms of properties of the final boards. Since hemi-cellulose was partially degraded, and fiber cell became easy to swell, fiber quality was accordingly improved while excessive destroying of xylanase pretreated fibers avoided. The fibers had the longest average fiber length and the largest length-to-width ratio. On the other hand fibers from sulphite treatment released the most free radicals since straw lignin was activated. The fibers pretreated by acetic acid demonstrated that acid pretreatment did not remove straw wax and silicon dioxide, but it changed pH value and buffering capacity of the surface of the straws. This helped straw to be easily bonded with UF resin. The boards showed better properties using above three methods than that using hot-water softening especially the internal bond (IB) strength.