Abstract: Rate of photosynthesis and growth of Gracilaria verrucosa in different layers of seawaters in Shanwei Wan was observed in our experiments in 1962 and 1980 respec-tively. The results obtained from these experiments are almost the same. 1. When the algae was reared near the surface layer of seawaters, the rate ofphotosynthesis and growth was fast. On the contrary if it was reared in the lower layerof seawaters, their rate of photosynthesis and growth was slow. 2. There is a compensation layer of the depth of transparency in the sea waters.At this layer the amount of oxygen produced in the photosynthesis is slmost equal tothat consumed in the respiratory process of the algae. Below this depth of transparencyin seawaters, the growth of the algae nearly stopped. In order to get a good harvest in the artificial raft cultivation, Gracilaria shouldbe float near the surface of seawaters. If the transparency of seawater is high, thealgae should be cultivated on the ropes hanging from the raft to proper depth, thelength of the ropes should not exceed 1.5 meter.