The effects of Alkali/alkaline earth metals (AAEMs) removal and KOH addition in char on formation and distribution of wheat straw pyrolysis products during volatile-char interactions were studied in a fixed-bed reactor. The results showed that after AAEMs removal from char, significant interactions between volatiles and char still existed, as its non-condensable gas yield greatly increased with less detectable organics observed in bio-oil compared to pure wheat straw pyrolysis. XPS results indicated that more aromatic carbon structures (C-Cprimary) were exposed on char surface after AAEMs removal, which might act as active sites during the interactions. KOH addition in char exhibited much bigger cracking performance than its interior K in char, resulting in a significant reduction in bio-oil yield and a great increase in non-condensable gas yield. KOH addition in char might promote decarboxylation, decarbonylation and sugar-ring opening reactions, leading to the decrease of linear acids and carbonyls and anhydrosugars and the increase of phenols and other aromatics in bio-oil. The cracking/decomposition of furans, cyclopentenones, and phenols and other aromatics would also be largely enhanced with the increasing amount of KOH addition. In addition, KOH in char could act as a catalyst for the char self-reforming by volatiles during the interactions.