The secretion of proteins depends on signal peptide. Gene trap is a powerful tool for functional gene identification and characterization. Classical gene trap employs geo as the reporter, and gives no discrimination on the types of trapped genes. A new reporter gene named peo was obtained by in turn fusing Exotoxin A of Pseudomonas aeruginosa, 2A sequence, transmembrane region of IL-2 receptor and neomycin phosphotransferase genes, Peo is able to report genes encoding secretory proteins specifically. To prove peo's specificity for secretory proteins, three plasmid vectors, representing three types of sequences possibly trapped by gene trap vector during screening, were constructed based on peo reporter. After transfecting HeLa cells with these plasmids, followed by G418 selection and PLAP staining, it is shown that the new vector could distinguish secretory proteins from others, and the gene trap vector taking peo as the reporter can trap secretory protein genes efficiently.