Abstract: Adhesion of bacteria to cell surfaces is the first step in infection, in which adhesin plays an important role and is a vital virulence factor for pathogens. A new kind of adhesins, trimetric autotransporter adhesins (TAAs) which are derived from Gram-negative bacteria, is found. TAAs are multifunctional proteins widely existing in Proteobacteria, secreted on cell surface by Ⅴ-type bacterial secretion system. TAAs have striking differences in size and amino sequence, but are surprisingly similar in molecular structure; they both have a trimetric surface structure with a head-stalk-anchor architecture which is like a "lollipop". The review describes the structure, secretion mechanisms and regional functions of TAAs to provide references for further study.