Abstract: Degenerate primers were designed using CDS sequences of homologous genes and the γ-glutamylcysteine synthetase gene LpGCS was cloned from perennial ryegrass (Loliumperenne) using RT-PCR and RACE techniques, with leaves of ‘Top hat Ⅱ’ as the test material. The full-length sequence of LpGCS gene was 1674 bp (GenBank accession number: KJ551844) with a complete open reading frame (ORF) of 1125 bp. Amino acid sequence identity, structure and homologous sequences with amino acids of 8 other homologous genes were studied and predicted. The protein molecular weight was 42.86 kDa (unstable protein) and its main secondary structure being an alpha helix. The protein amino acid sequence had relatively high homology with 8 other homologous amino acid sequences and had higher homology with graminaceous plants, such as wheat (Triticum aestivum), stiff brome (Brachypodium distachyon) and Japanese rice (Oryza sativa Japonica Group). In addition, sense and antisense plant expression vector pCAMBIA-Ubi-LpGCS+ and pCAMBIA-Ubi-LpGCS- were successfully constructed and transgenic tobacco obtained by agrobacterium mediated transformation. The transgenic tobacco with LpGCS+ grew faster and flowered earlier than the transgenic tobacco with LpGCS-. Exposed to Cd²⁺ stress (10 days), physiological and biochemical tests of transgenic and wild-type tobacco showed that the MDA content of LpGCS+ transgenetic plants was lower than the wild type, and POD, SOD and CAT activity higher than those of the wild type. In contrast, the MDA content of LpGCS- transgenetic plants was higher than the wild type and POD, SOD and CAT activity lower. In summary, overexpression of the LpGCS gene in tobacco plants could improve resistance to Cd²⁺ stress and lay the foundation for the genetic transformation of perennial ryegrass cultivars able to tolerate heavy metals.