Abstract: 【Objective】 To analyze whether some transcription factors in Arabidopsis thaliana, known for the secondary cell wall thicken, could regulate the expression of the key genes of xylosyltransferase, such as FRA8, IRX9, IRX10, IRX14, F8H, IRX9-L, IRX10-L and IRX14-L, and observe the phenotype of KNAT7 dominant repression plant.【Method】 Effectors and reporters were constructed by Gateway Technology and the transient transcriptional activation assay was conducted. Construct pCAMBIA1304-p35S∷KNAT7-SRDX recombinant plasmid by Gateway Technology and transform this plasmid into wild A. thaliana via Agrobacterium tumefaciens-floral dip method．【Result and conclusion】 The transient transcriptional activation assay revealed that transcription factors KNAT7, MYB46, ERF72, SND1, NST2 could activate the expression of a number of the key genes of xylosyltransferase. KNAT7 could activate the expression of FRA8, IRX9 and IRX14-L. Furthermore, dominant repression of KNAT7 significantly affected the growth of Arabidopsis thaliana. These results indicate that KNAT7 probably plays an important role in the regulation of xylan biosynthesis.