Vegetation succession can significantly affect soil microbial biomass, yet how soil physicochemical variables impact the relationship between vegetation succession and soil microbial biomass is not well understood. The current study investigated the effects of vegetation succession on soil microbial biomass at various soil environments based on the “space-for-time” assumption at the lakeshore wetlands of Lake Poyang, China. We collected soil samples at 0-10 cm depth increment at mudflat belts, hygrophilous vegetation belts, and emergent vegetation belts on four typical lakeshore wetlands (including Lake Banghu and Lake Dahuchi which had barren soils and Lake Donghu and Lake Baishahu which had fertile soils). Soil microbial biomass carbon (MBC) and microbial quotients (qMB) were used to indicate soil microbial biomass. Lakeshore wetlands at Lake Banghu, Lake Dahuchi, Lake Donghu and Lake Baishahu had average soil MBC of 1077.27, 888.29, 942.45 and 1162.46 mg/kg, respectively, and mean soil qMB of 6.07%, 6.17%, 3.60% and 3.79%, respectively. Along the mudflat-C. cinerascens-M. lutarioriparius succession, soil MBC firstly increased and then decreased. However, along the mudflat-C. cinerascens-P. australis succession, soil MBC continually increased. Vegetation succession did not significantly influence soil qMB. Although plant growth promoted soil MBC at all lakeshore wetlands, the increments at two relatively infertile lakeshore wetlands (Lake Banghu and Lake Dahuchi) were much higher than those at two relatively fertile lakeshore wetlands (Lake Donghu and Lake Baishahu). Soil qMB at Lake Banghu and Lake Dahuchi were significantly higher than those at Lake Donghu and Lake Baishahu. Soil MBC and qMB were determined by soil pH and soil carbon, nitrogen or phosphorus contents, but the key elements were varied among the four lakeshore wetlands. The results proved that the effects of vegetation succession on wetland soil microbial biomass not only depended on plant species, but also had close relationships with soil physicochemical variables. Our study was helpful for understanding the change mechanism of soil microbial biomass in wetland ecosystem, and could be used to improve the management in the floodplain lakes in the middle and lower reaches of the Yangtze River.