By analyzing the cDNA sequences of carboxyltransferase alpha subunits(α-CTs) from Arabidopsis thaliana and Glycine max,and combination RT-PCR, 3′-rapid amplification of cDNA ends (3′-RACE) and Genome walking techniques, the full length cDNA of plastid α-CT from embryos of Brassica napus between 20 and 29 days after flowering was cloned. Homologous analysis showed that the amino acid sequence deduced from it shares 85% and 59% homology with those of α-CT in Arabidopsis thaliana and Glycine max, respectively. The sequence encoding mature peptide that was absent from chloroplast transit peptide has been inserted into expression vector pHBM625 and expressed successfully in Escherichia coli by Western blotting analysis.