Abstract: In this study, we optimized the technology of the large-scale seeding and breeding of Sargassum vachellianum in the sea water. The mature algae were collected from the sea water and then were stimulated to spawn the fertilized eggs. These eggs were collected and sprayed onto the substratum surface of the floor slab, the coir rope and the plank for the further settlement, germination and growth. The results suggested that the coir rope was the most efficient for seeding. Ten days after the spraying, the germination rates on the three substrates were 85.5%, 80.2% and 91.3% respectively, and the average height was 1.3 mm. On the 20th day, the plank-attached seedlings showed the highest density of 8.2 cells/cm2, but the growth was slow. On the 30th day, the branches of the seedlings appeared and the growth rate was 1.6 times higher than that on the 20th day. The height of seedlings on the coir rope was the greatest and the survival rates on the three substrates were 83.6%, 79.7% and 75.6% respectively. On the 60th day, the coir ropeattached seedlings showed the highest values in density and in the average height. When transferred into the sea water, the floor slab (algal reef)-and coir rope-attached seedlings grew faster in the turbulent and torrential area. After 4 weeks, the average heights of plants on the floor slab and the coir rope were 98.7 mm and 103.1 mm respectively, which was 1.5 times higher than the control group. However, the seedlings on the coir rope could be easily washed away in the sea water. In conclusion, the algal reefs could be the suitable substrate for the large-scale farming and they may also be an ideal material for the repair and reconstruction of the algae bed.