X-ray-based measurements of crystallinity index (CrI) indicated that pretreatment increased crystallinity of corn stalk, and a max- imum was reached at 21 day of pretreatment (Table 1). The crys- tallinity of corn stalk bio-pretreated for 21 days was 18.4% higher than that of un-pretreated corn stalk. Comparing CrI of corn stalk with MOE and MOR of the fiberboard, there was a positive correla- tion between CrI of corn stalk and MOE and MOR of the fiberboard, which indicated that bio-pretreatment could increase the CrI of corn stalk as much as possible in order to enhance the mechanical properties of the fiberboard.