Abstract: A series of culture experiments of the subtidal brown alga Sargassum horneri was performed during 2005~2007, including development of receptacles, discharge of eggs, impact of environmental factors on the development of the zygotes. Artificial seedlings derived from zygotes were obtained from selected individuals sampled from wild populations at Nanji Island, Zhejiang Province, China. Different substrates were tested for settlement of zygotes. Field in situ observation of the growth and reproduction of selected individuals was performed. Based on these results, we concluded that field population of this alga sustains itself principally through sexual reproduction. These results lay the basis of artificial seedling reproduction of this alga.