Two layers of ancient paddy soil were discovered in archeological excavation of Chuodunshan Relics in Kunshan,China.One of them could ascend to 6 500 a BP (prehistoric),and the other 3 320 a BP (Shang-Zhou Period).Two soil profiles,not far apart,named P-01 (containing both soil layers) and P-03 (containing only the latter) respectively,were fixed and soil samples were collected according to soil color and texture.The techniques of soil anaerobic incubation,Biolog analysis and PCR-DGGE of 16S rDNA gene fragments encoding Euryarchaeota variable V3 region were used to study microbial diversity of anerobic microbes,methane emission potential and the genetic diversity of methanogenic archaea communities in different soil layers.The aim of this study is to determine biological properties of the ancient paddy soils.The results show that among all the underground soil layers of the two profiles,the prehistoric ancient paddy soil layer still had quite a number of anaerobic microbes surviving in the soil,up to 7.0×10⁵ cfu g^-1 soil,and it also showed better carbon utilization capacity and diversity than the other soil layers.A tendency was noticed that the prehistoric ancient paddy soil showed slightly higher methane emission potential than its parent material-lake sediment and homochronous non-paddy soil-loess,though it was very weak compared with that of recent paddy soils.PCR-DGGE analysis revealed that the methanogenic archaea community made paddy soil layers different from the other soil layers,and paddy soils of different ages have their respective special predominant populations.