The formation, release and germination of tetraspores, together with the morphogenesis of gametophyte of Kapphycus alvarezii were investigated in Lian Bay, Hainan Province, China from November, 2007 to April 2009. The results showed the brown Kappaphycus alvarezii, originally gained from Phillippines in 1985, were tetrasporophytes and the tetraspores were mainly formed and released from April to October. Both tetraspore germination and embryogenesis could be induced artificially in the laboratory and great variations of embryos in color from brown red, yellowgreen, olivine green to olivinebrown chimera were observed. Rhizoids were formed and then disappeared during the embryogenesis period. The germination rate of tetraspores was about 87.1%±7.2% and the mean specific growth rate of embryos was about 6.3%±1.1 %/d for indoor dish culture. After 160 days indoor cultivation, the germinated tetraspores developed to young gametophytes. Then, 20 young gametophytes were cultured on the soften raft in the sea. The average specific growth rate measured was over 10%/d in the first month culture in the sea, and the highest specific growth rate for young gametophytes was over 21.2 %/d. However, the specific growth rate gradually reduced accompanied with the frond increase in size in the following cultivation. Four types of gametophytes with different morphology, density of branches and growth rate were obtained as follows: TypeⅠ shows thick buds, cylindershaped trunk, taper terminal, and sparse branches. Type Ⅱ shows thin buds, cylindershaped trunk, blunt terminal, sparse branches. Type Ⅲ shows thin buds, cylindershaped trunk, taper terminal, and dense branches. Type Ⅳ shows thin buds, cylindershaped trunk, oblate terminal stem, taper terminal, and dense branches. During our experimental period, a large scale of iceice disease broke out, and the vitality and resistance to the iceice disease in some strains of the gametophytes improved significantly compared to their parent plants.