, which has rich agar, comprises the third-largest seaweed cultivation industry group in China, after . As light intensity gradually strengthens in summer, in the surface layer of cultivation areas becomes green, or even white, yet the internal part remains dark red. was cultured in artificial seawater with inorganic nitrogen (NO₃^-:NH₄⁺=2:1). Three conditions:low light low nitrogen (L-N-), high light low nitrogen (L+N-) and high light high nitrogen (L+N+) were settled in this study. The impact of light intensity and nitrogen on physiology and metabolism of was studied through measured matter accumulation, photosynthetic pigment, key enzyme during carbon and nitrogen metabolism under three conditions. The results showed that, compared with the L-N-group, the L+N-group showed decrease of soluble protein, water, phycoerythrin and chlorophyll-a, but the amount of soluble sugar increased 13.67%. Compared with the L+N-group, the L+N+ group showed the increase of soluble protein, water, phycoerythrin and chlorophyll-a, but the amount of soluble sugar decreased 16.3%. Compared with the L+N+ group, the L-N-group showed the increase of soluble protein, phycoerythrin, but there is no significant difference in its amount of water content, chlorophyll-a and soluble sugar. These results confirm that a sufficient amount of nitrogen can weaken the negative effects of high-intensity light on a red macroalgae.