Abstract: Porphyra haitanensis is an economically important marine crop in southern China.To study the molecular mechanism of high temperature tolerance in P. haitanensis,the technology of annealling control primer(ACP) was used to screen the differentially expressed genes in F₄ generation gametophytic blades of a high temperature tolerance line Z-61.The primer combination of dT-RSL and RSL7 amplified one differentially expressed gene fragment.After sequence analysis,the gene fragment was proved to be the full length sequence of ribosomal protein S7 gene,and then it was named Phrps7 (acceession number JF719273).The Phrps7 gene of 702 bp contains an open reading frame of 585 bp encoding a PhRPS7 protein of 195 amino acid.The PhRPS7 protein assembled by 5 helix,6 sheet and 6 cycle shared high sequence identity with RPS7 proteins from other organisms(>55%),and its molecular formula was C₉₈₄H₁₆₀₄N₂₉₄O₂₈₃S₂.Phylogenetic analysis showed that the PhRPS7 protein has closer relation with RPS7 proteins from epiphyte than those from other organisms.The results of real-time quantitative PCR indicated that the expressed level of Phrps7 has high relationship with high temperature stress.At the beginning of high temperature stress(0-6 d),the expression of Phrps7 gene was up-regulated significantly,but at the later stage of high temperature stress(>6 d),the expression of Phrps7 gene was down-regulated,however,it was still higher than that at the beginning.