To explore the influence of suitable amounts of straw returning on soil quality and crop yields for middle region of Jiangsu, a field experiment was conducted to determine the effects of different amounts of straw returning on soil nutrients, carbon pools and crop yields in rice-wheat rotation system. After five-season continuous straw returning, the results showed that: 1) straw returning increased the contents of soil total nitrogen, available phosphorus and rapidly-available potassium, and 75% of five-season continuous straw returning got greatest increases, by 3.54%, 3.97% and 10.28%, respectively. 2) 75% of five-season continuous straw returning significantly increased the contents of soil total organic carbon, while 50% and 75% five-season continuous returning significantly increased the contents of water-soluble organic carbon and easily oxidizable carbon, and the effect was the same on soil available carbon contents and carbon pool management index. 3) Straw returning increased annual crop yield in an order of both rice and wheat straw returning>only one crop straw returning>no straw returning. Among them, 75% of five-season continuous straw returning significantly improved the yields, increased by 10.01%. In conclusion, the treatment of 75% of straw returning is most suitable in a rice-wheat rotation system of the study region.