Although the thin-blade strain (HR-5) of Pyropia haitanensis could be cultivated in the south coast of China, the effect of low-salt tolerance on it is not clear. In this study, the conchospores and blades of the wild cultivated strain (WT-10) of P. haitanensis and HR-5 strain were cultured in media with salinity of 26‰, 10‰, and 3‰, respectively. The results illustrated that: After being cultured for 7 days, the survival percentages of conchospores were not significantly different between WT-10 and HR-5 at the salinity of 26‰ and 10‰ (P > 0.05), but the survival percentage was 60.8% higher in the latter than in the former at the salinity of 3‰ (P < 0.01). When the 25-day-old blades of WT-10 and HR-5 were cultured at the salinity of 26‰, 10‰, and 3‰ for another 20 days, the specific growth rates of the blades length in HR-5 were similar to WT-10, respectively. The contents of total phycobiliprotein of the HR-5 were 127.9, 88.7, and 83.0 mg/g, respectively, which were 1.8, 1.7, and 2.1 times those of the WT-10, showing highly significant differences (P < 0.01). In addition, with the decrease of culture salinity, the Fv/Fm values of WT-10 and HR-5 gradually decreased, but the reduction rate between the two strains was not significantly different (P > 0.05). The above results indicated that the low-salt tolerance of conchospores and blades of HR-5 was not weaker than that of WT-10, which provided a theoretical basis for the management mode when continuous precipitation was encountered in the cultivation process of HR-5 strain.