This study is intended to clone CAD from ramie (Boehmeria nivea L. Gaud. cv Xiangzhu 3), and analyze the expression patterns of CAD in stems from 4 representative ramie cultivar. First, the cDNA sequence of CAD were identified by analyzing the transcriptome data of ramie cultivar Xiangzhu 3 and cloned by RT–PCR combined with RACE method. Secondly, the qRT–PCR was carried out to analyze the expression levels of CAD transcripts in 4 ramie cultivars: Xiangzhu 1, Xiangzhu 3, Xiangtaidayebai and Chengbuqingma. Finally, lignin contents among different cultivars were visually analyzed by histochemical staining of transverse sections of ramie stems using the phloroglucin. The BnCAD cDNA sequence was 1 378 bp in length (GenBank accession number, KF758396) and could be translated into a putative protein with 359 amino acids. Blast and protein structure analysis showed that this cDNA sequence is in high homologous with other plant CAD gene, and with 97% homology compared with Medicago truncatula, which confirmed that this cDNA sequence was the CAD gene. qRT–PCR analysis revealed that the expressions of CAD was much higher in phloem than xylem in Xiangzhu 1 and Xiangzhu 3, while Chengbuqingma the opposite, and no obvious difference was observed in Xiangtandayebai. Histochemical lignin assays showed that the staining degree between different cultivars is directly proportional to the quantitative expression of CAD transcripts, suggesting an important role of CAD during ramie lignin synthesis.