Abstract: MATH domain,refers to the Meprin and TRAF-C homology domain, which consists of 7-8 anti-parallel β-sheet. AtSb3，an unknown function gene，encodes a protein with dual tandem MATH domains in Arabidopsis thaliana.Based on the construction of the vector with AtSb3 gene promoter and GUS fusion expression cassette and obtaining of transgenic lines of Arabidopsis thaliana.The tissue localization of AtSb3 gene expression was investigated by semi-RT-PCR and histochemical stain. The corresponding results showed AtSb3 gene expressed not in the root,stem,leaf,flower and silique but only in roots.The results of GUS staining showed that, in just germinating seed，AtSb3 gene only expressed in radicle. In cotyledon expansion period after seed germination, AtSb3 gene was only found in root tip, not the other parts of a plant. In 4 to 5 leaf stage seedling, there is no expression of AtSb3 in aboveground parts but in taproot and lateral root and the region close to root-stem converse zone indicated by the blue. In the root tip, the overlapping portion of the root cap and meristematic zone, as well as enlongation zone were stained deep blue, which means AtSb3 gene expressed higher in these parts, whereas the region between overlap and enlogation zone was stained very light, implicating AtSb3 gene expressed very low in the part.