Abstract: Grateloupia corymbcladia Li et Ding and G. subpectinata Holmes distributed in Nanji Island, Wenzhou City, Zhejiang Province (specimen of origin) were studied in detail using molecular-assisted alpha taxonomy (MAAT). The results showed that: (1)G. corymbcladia were upright, purple-red, cartilage and 15—30 cm height. The main branch was flat, and the end was elongated to a sub-flat shape with 2—5 mm wide. Branchlets and 1—2 pinnate branches were distributed on both sides of the main branch. The reproductive structure of the female gametophyte included carpogonial branch ampullae and auxiliary cell ampullae, which were composed of five cells and four cells (Grateloupia type), respectively. Mature tetrasporangia originated from inner cortex cells and split into cross. The above characteristics were consistent with G. subpectinata. (2)Under laboratory conditions, the female gametophytes of G. corymbcladia and G. subpectinata both produced and divided to form discoids. The spore development types were all “mediate discal type”. (3)Based on the results of rbcL and COⅠ gene sequence analysis, there were no pairwise divergence between the six samples of G. corymbcladia and the G. subpectinata. They all formed a single monophyletic subclade. These results indicate that G. corymbcladia and G. subpectinata were the same species, and G. corymbcladia was regarded as the synonym of G. subpectinata.