Abstract: In order to explore the taxonomic value of the ultrastructure of bark beetles, the ultrastructure of seta on pronotal end in 53 species of bark beetles(Scolytinae: Curculionidae) and other 6 species beetles of Curculionoidae was analysed in this study. The analysis showed obvious similarity within the genus and interspecific difference among 6 species of Pityophthorus and Ips, 5 species of Xyleborus, 3 species of Orthotomicus respectively. It was inferred that these marginal seta could be available character in classifying these bark beetles. The ultrastructures of seta of other 6 species beetles of Curculionoidae are different: those of Cylas formicarius are absent, Araecetus fasciculatus single, Sipalus gigas multi-branched, Rhabdoscelus obscurus palmate, Euplatypus parallehus and Euplatypus hintzi bifurcated, similar to that of Scolytini. In addition, it was discovered that it had an evolutionary trend which these seta on pronotal end were from none to appear, palmate to bifurcated form, complex to simple, after systematic analysis of the microstructure of marginal setae of 53 species of bark beetles belong to 28 genera in 14 tribes of subfamily Scolytinae and 6 other species of Curculionoidae. The results show that the ultrastructure of seta on pronotal end can be used as an available feature in bark beetles classification and has certain evolutionary research significance.