Abstract:The selection of a suitable reference gene is a critica1 condition for improving the precision of gene expression analyzing by quantitative real time PCR(qRT-PCR). The 18S rRNA gene which has a broad and constant expression was always used as reference gene for qRT-PCR. The study was to obtain the 18S rRNA gene of luffa and design the qRT-PCR primers. Through PCR and sequencing, the 18S rRNA gene of luffa was cloned firstly. It was 1 862 bp long and the GenBank accession number was KM656452. A pair of qRT-PCR primer was designed based on the 18S rRNA gene sequence showed, high specificity and amplification efficiency. The RT-PCR indicated that the 18S rRNA gene was stable expression under abiotic stress and in different growth stages, so it was suitable as a reference gene for the analysis of gene expression patterns in luffa. The present study has provided an important reference for analysis the expression of critical genes in luffa.