The AOP2.1 gene is an important gene affecting the side chain modification of aliphatic glucosinolate. Here, the Brassica oleracea var. capitata AOP2.1 (BocAOP2.1) gene sequence was obtained from the Brassica database (BRAD) and subjected to sequence analysis. It is indicated that the BocAOP2.1 gene contains a 1,320 bp open reading frame (ORF) encoding a protein of 439 amino acids with a calculated molecular weight of 48.28 kD, the isoelectric point (pI) is 5.36. The highest number of amino acids is Valine (Val), whereas the lowest number is Tryptophan (Trp). Its prediction formula is C2109H3347N589O682S13. Its total hydrophilicity index is −0.472, the solution instability index is 31.63, and the fat solubility index is 79.23. Sequence alignment indicated that the BocAOP2.1 protein is more closely related to Brassica napus and Brassica juncea, those all belonged to the Cruciferous genus. The results of this study provide a molecular basis for elucidating the function of BocAOP2.1 gene in cabbage.