Porphyra haitanensis is one of the most important cultivars of marine algae in China,but its production and quality can be significantly jeopardized by execrable environments such as high temperature,therefore,selection of a heat-resistant strain will greatly benefit the nori industry. To this end,in the present study,we selected a meliorated strain Q-1 which has significant heat-tolerance to 30 ℃. Upon further characterizing the cultures of strains Q-1 and WT at 28 and 30 ℃,we show here that in a period of 15 days,the Q-1 conchospores survived at rates of 76.8% and 60.1%,respectively,while the WT conchospores survived at much lower rates of 15.9% and 6.7%. The Q-1 conchospores also divided at significantly higher rates of 100% and 83%,as compared with those of 90.4% and 63.8% for the WT conchospores,respectively. When the 35-day-old conchospore germlings were cultured at 24,28 and 30 ℃ for 25 days,the mean length of blades increased 19.4,10.8 and 2.8 times for Q-1,and only 7.3,1.7 and 0.9 times for WT compared with the original mean length,respectively. At 24,28 and 30 ℃,the blades of strain Q-1 grew 1.5,4.8 and 0.9 times faster than those of the WT,the blades of WT strain began to decay after being cultured for 15 days,however,the blades of Q-1 strain did not decay even being cultured for 25 days. The blades of Q-1 strain also showed excellent high-temperature tolerance during its large-scale cultivation in sea area. In the last autumn,the high temperature (28-30 ℃) continued for about two months after conchospore-seeding of Porphyra haitanensis,the blades of the WT decayed on a large scale and the production decreased significantly; while the blades of the Q-1 grew normally with rapid growth and did not decay,and the production was much higher than that of the WT. The above results indicated that the strain Q-1 is a fast growing and heat-resistant strain that may offer broad applications for the nori industry.