Two strains of Pyropia haitanensis ("Native Dongtou" and "Eastern Zhejiang NO.1") were selected as research materials in Dongtou aquaculture district. The thallus length, dry weight, CNP content were determined at different harvest stages, as well as the S value, yield, and sequestration efficiency of carbon, nitrogen and phosphorus were calculated. The results showed that with the extension of harvest time, the thallus length of two strains of Porphyra haitanensis decreased gradually, the dry weight and S value of single thallus increased gradually, the yield increased first and then decreased, and the sequestration efficiency of CNP increased as a whole. The length and dry weight of single thallus of "Native Dongtou" from the first harvest to the fourth harvest were higher than those of "Eastern Zhejiang No.1". The yield and CNP sequestration efficiency of "Native Dongtou" from the second harvest to the fourth harvest were higher than those of "Eastern Zhejiang No.1". There was no significant difference in S value between the two strains of Porphyra haitanensis. The total sequestration efficiency of CNP for "Native Dongtous" from the first harvest to the fourth harvest was 900.74 kg/hm², 110.16 kg/hm², 14.16 kg/hm²,respectively. The total sequestration efficiency of CNP for "Eastern Zhejiang NO.1" was 683.34 kg/hm², 84.3kg/hm² and 10.75 kg/hm², respectively. The above indexes showed extremely significant difference among different harvest stages (P<0.01), but no significant difference between different strains (P>0.05). The results are helpful to further understand the growth characteristics and ecological benefits of Porphyra haitanensis culture.