The intertidal green macroalgae Ulva linza and Ulva prolifera were selected to study the effects of carbonic anhydrase inhibitors AZ and EZ on the photosynthesis of the thalli under different temperatures. Six temperature levels were set (5, 10, 15, 20, 25 and 30℃) in the experiment. Our results showed that the values of pH compensation point of both Ulva linza and Ulva prolifera was as high as 10. This suggested that the both the two Ulva species possessed rather high ability of photosynthetic acquisition of inorganic carbon. The ability of inorganic carbon acquisition in both the two species were significantly affected by temperature, and this temperature responses were species-specific. Compared with Ulva prolifera, Ulva linza was more sensitive to temperature, suggesting that the optimum range of temperature for photosynthesis was narrower in Ulva linza than Ulva prolifera. At high temperature (30℃), the net photosynthetic rate of Ulva linza was decreased by 56%, while only by 20% in Ulva prolifera, compared with the rate at optimum temperature. These results suggested that Ulva prolifera possessed stronger ability to endure high temperature than Ulva linza did. This might be one of the most possilble physiological reasons that the dominant species in green tide bloom is Ulva prolifera. For Ulva linza, the transport of inorganic carbon was predominantly carried out by catalysis of extracellular carbonic anhydrase at temperatures of 5℃ and 30℃. However, no significant effect was found in the transport of inorganic carbon at temperature of 15℃ when the extracellular carbonic anhydrase inhibitor AZ was added. This implied that, at 15℃, another way of transport of inorganic carbon might eliminate the effect of the inhibition of extracellular carbonic anhydrase. Over the temperature rang of 20-25℃, extracellular carbonic anhydrase-mediated inorganic carbon transport and the other patterns of inorganic carbon transport operated as a fixed proportion, respectively. For Ulva prolifera, the primary pattern of the transport of inorganic carbon was not due to the catalysis of extracellular carbonic anhydrase at temperature of 5℃, and another pattern of inorganic carbon transport might operate at this temperature. However, as temperature rose to 10℃, the action of catalysis of extracellular carbonic anhydrase increased significantly, and this action maintained the same levels with further rising of temperature.