Abstract: We investigated the effects of different light intensities (2 000 lx, 4 000 lx, 7 500 lx, 10 000 lx, 15 000 lx), temperatures (15 ℃, 20 ℃, 25 ℃, 30 ℃, 35 ℃) and salinities (5, 10, 15, 20, 25, 30, 35) on the growth and biochemical constituents of Hypnea cervicornis. The suitable conditions for the growth of H.cervicornis were light intensity of 2 000~4 000 lx, 20~30 ℃ and salinity of 25~35;the optimum conditions were light intensity of 4 000 lx, 25℃ and salinity of 30, under which H.cervicornis obtained the maximum relative growth rate (RGR) and the lowest SOD activity. The contents of soluble protein (SP), chlorophyll a (Chl-a) and carotiniod (Car) decreased while those of phycoerythrin(PE) and phycocyanin(PC) increased with increasing light intensity within light intensity of 4 000~15 000 lx. Under conditions of 25~35 ℃ and salinity of 30~35, the contents of soluble protein, chlorophyll a, carotiniod, phycoerythrin and phycocyanin decreased with increasing temperature and salinity, which indicates that optimum temperature and salinity can promote the accumulation of biochemical components of H.cervicornis.