Hainan is the second largest and southernmost island of China, and it harbors many species of the family Gracilariaceae. In this study, we conducted molecular and morphological analyses of gracilarian specimens collected from Hainan Island, to clarify their taxonomic identity and phylogenetic relationships. Five species of Gracilariaceae in Hainan were determined through maximum likelihood and Bayesian analysis of rbcL sequence data. Based on the phylogenetic trees and morphology, Hainan specimens were identified as three species of Gracilaria, one species of Gracilariopsis, and one species of Hydropuntia, namely, G. salicornia, G. tenuistipitata, Gracilaria sp., Gp. bailiniae and H. edulis. This is the first report of the molecular phylogeny of Gracilariaceae on Hainan Island, and it helps to clarify the taxonomy and distribution of gracilarian species in the Asia-Pacific region.