In order to study the effects of total rice and wheat straw returning on the paddy soil ecological environment in wheat-rice crop rotation system，the high-throughput sequencing technology was used to compare paddy soil physical and chemical properties and bacterial community structure characteristics under four straw returning modes:rice and wheat straw no returning( CK)，rice straw returning in wheat season(W-RS)，wheat straw returning in rice season(R-WS)，both rice and wheat straw returning( RWS).The results showed that，compared with CK，returning straw increased the contents of soil organic matter，nitrogen，phosphorus and potassium，with greater increase observed in RWS treatment as well as in 0 ～ 5 cm soil layer.The soil bacteria Sobs and Shannon index were not affected by straw returning.In all treatments，the top three dominant bacteria phyla were Proteobacteria，Acidobacteria and Chloroflexi，accounting for 38.9%，17.0% and 14.1% of the total sequence，respectively.The bacterial phyla with significant differences among treatments belonged to the rare phyla whose relative abundance were less than 0.5%.Soil organic matter，soil moisture content，total phosphorus and total nitrogen content represented the key soil physical and chemical properties that affected bacterial diversity in all soil layers.In conclusion，at the annual scale，straw returning to the field could change soil physical and chemical properties and thus affect soil bacterial community structure，especially the rare bacterial taxa.