Abstract: Flowering phenology of Betula alnoides under different site conditions was observed and compared at inflorescence, individual and stand levels in an ecotone of two types of soils originated from limestone (site L) and granite (site G), respectively, at Jingxi County, Guangxi. The flowering of both male and female inflorescences lasted two to three days, and male inflorescences normally bloomed approximately fourteen days earlier than female ones at the same positions on a tree. At individual level, flowering lasted four to twenty eight days with flowering synchrony index of Augspurger (1983) ranging from 0.160 to 0.259 in each plot, and majority of trees flowered initially upper canopy, followed by middle and lower parts. There existed no significant difference of flowering duration and synchrony between individuals of site G and L (P＞0.05). And flowering lasted forty to fifty eight days without significant difference of flowering duration between both sites at stand level.