The results showed that the three red seaweeds were similar to the eulittoral species in photosynthetic properties, having higher light saturation points 600 – 1000 μE/(m²*s) and light compensation points 12 – 40 μE/(m²*s) of photosynthesis as well as higher temperatures (>=25°C) for photosynthesis. Their photosynthetic and respiratory rates were significantly affected by temperature, with the high values at 25°C. The temperature coefficients of respiration of the red seaweeds were 1.4 - 5.5 at 5 - 15 °C and 1.1 - 2.7 at 15 - 25°C, and at the favourable growth temperatures, the net photosynthetic rates were 4.90 O₂ mg/(g*h) for Chondrus sp. and 8.14 O₂ mg/(g*h) for Gracilaria asiatica at 15°C, and 11.87 O₂ mg/(g*h) for Gelidium amansii at 25°C . The net photosynthetic rate of the immature G. arnansii in autumn was 19.19 O₂ mg/(g*h) at 25°C and 1000μE/(m²*s). Therefore, Gelidium amansii has an unexpectedly high efficiency of photosynthesis and it seems as if the low growth rate in its habitat is caused by low light intensity and low temperature, so the productivity might be raised even higher under certain artificial culture conditions of higher light intensity and favourable temperature.