Abstract: A red color alga, Protosiphon botryoides was collected from the beach of an island in Yangtze River, Wuhan, China.It is a new record of China. We cultured it on BG11medium agar successfully. Many swimmers had escaped from red coenocysts after flooded with water,each swimmer has two equal-length flagella; some of them lost their flagella and stigma soon, then became quiescent without copulation and formed new vegetative cells; other swimmer cells may function as isogametes. Zygotes are stellate form or variously lobed. The young vegetative cells are round, parietal chloroplast is reticulate with one pyrenoid. They grow bi-directional, the upper is spherical with diameter up to 200μ m; the lower is colorless rhizoid,length up to 1mm. Upon maturity, the sacs of Protosiphon contain many pyrenoids and are multinucleate. Bud reproduction was found from some round vegetative cells, namely a new sacwithout the rhizoid separated from the parent sac by septa, but, it was very different from the literature that the new sac was almost same size as the parent sac. For the systematic position,the bud reproduction is a type of vegetative cell division, so it should not belong to Chlorococcales, which lost the capability of vegetative cell division;no siphonaxanthin and siphonein were found from Protosiphon, so it is not reasonable to be in Siphonales too. Protosiphonales may be the best destination for this genus, but further investigations are required.