Crop type is one of main factors influencing weed community structure.  However, the identity of weed communities associated with the cultivation of different crops in farmlands remains largely unclear.  A field survey of weed seed banks was conducted in 2 280 fields at 228 sites of 62 locations representing three different types of farmland (95 paddy, 73 summer-ripe, and 60 autumn-ripe farmlands) along the bank of the Yangtze River in Anhui Province, China.  A total of 43 families and 174 species of weeds were found in these weed seed banks.  A comparison of the composition of weed groups in the seed banks showed that the species number and density percentage of grass, sedge and broadleaf weed groups were similar among the different types of farmland.  The seed banks of all three farmland types shared 71 common weed species, accounting for 40.80% of the total number of species.  These common weeds, which were both associated and not associated with crops, accounted for 91.71% of the total dominance degree among all farmland types.  The crop-associated weed species were distributed in all soil layers of each farmland type.  The Shannon-Wiener index H´ (description of species diversity which is more sensitive to dense species) and Pielou’s evenness index J (description of species evenness) in summer-ripe farmland were similar to those in autumn-ripe farmland but differed from those in paddy farmland.  However, the Simpson’s index D (description of species diversity which is more sensitive to sparse species) was similar among all three farmland types.  The results of similarity comparison indicated that although the aboveground weed community differed among the different cropping patterns, the weed species composition in the soil seed bank was still similar.  Consequently, our results demonstrate that after the implementation of long-term monoculture patterns, weed species compositions in the soil seed bank in different farmlands become homogenized regardless of the crop type.