Abstract: In order to establish artificial seeding techniques of Sargassum horneri, it was observed in this paper that release of eggs, embryology of zygotes, development and growth of juvenile sporophytes, and effect of culture conditions on germlings growth in laboratory culture. The results showed that the eggs released concurrently from the basal and middle section of female receptacles, and adhered to the surface of receptacles for fertilization and germination. Eight nuclei in a fresh released egg would intergrade after fertilization and then stated to nuclei fusion to form a larger central nucleus in the zygote. The zygote stated the first transverse division across the longer axis of the cell and produced a two-cell juvenile sporophyte, The second division transversely occurred near the one extreme of the juvenile sporophyte and produced a small cell named as “rhizoid original cell” which finally developed into rhizoids after several divisions. It took about 48 hours from the zygote to developed into multicellular germling with rhizoids through subsequent cell divisions. The mean length of Sargassum horneri germling was more than 3 mm and grew 2 leaflets within culture of 15 days. After 50 days of culture, these germlings grew up to 20 mm in the mean length and with 10 leaflets. During culture of the germlings, higher temperature and longer light length are of benefit to germling growth and increase of leaflet number. The germlings showed preferable growth at 21-24℃ under 40 μmol photons.m-2.s-1 and long-day (14L:10D).