The present paper aimed to study the expression of CT703 mRNA of Chlamydia trachomatis( Ct) serovars L2 under acute infection or persistent infection conditions in HeLa cells. Transmission electron microscopy ( TEM) was used to determine the establishment of acute infections and persistent infections. The expression of CT703 mRNA of Ct in HeLa cells was detected by reverse transcriptase-polymerase chain reaction ( RT-PCR) . Giemsa staining showed that there were enlarged and aberrant reticulate bodies ( RBs) in inclusions in persistent infections. The expression of CT703 mRNA of Ct in persistent infections was significantly lower than that in acute infections, which may be one of the mechanisms underlying the persistent infection of Ct in cells.