The brown macroalga Sargassum naozhouense is a native species of Guangdong Province,which has edible value,medicinal value and prospect to be exploited into a new cultivation species.Based on reproductive biology study from July 2009 to June 2010 in Xuwen,Zhanjiang,the seasonal variation of biomass and mean thallus length of S.naozhouense were investigated.S.naozhouense is a pseudopermanent,dioecious species with dimorphism receptacles.The growth pattern of S.naozhouense may be divided into inactivity period(from August to October),growth period(from November to midApril of next year),reproductive period(from mid-April to early-June)and senescence period(from early-June to late-July).The propagation and maintenance of field population was mainly based on regeneration seedlings of rhizoids that occurred every month in a year round,and the seedlings produced by sexual reproduction accounted for a quite low proportion.Removing holdfast suggested reducing population,but the same species’ standing stock of the same area and same time increased markedly next year if it is harvested by cut method.The wild population is located on rock within 2 m depth,5-10 m width of intertidal zone.After the earlyNovember,thalli grew faster and faster and reached the largest length to early-May.Seasonal variations of length and biomass were very obvious and shared the same pattern.The highest biomass of a permanent quadrat is 1 280 g/m²,the length of the maximum single plant can achieve 1.73 m,and the weight of the maximum single plant can be up to 250 g.