The effects of elevated atmospheric CO2 concentration on the rate of wheat straw decomposition and nitrogen distribution of decomposed straw in paddy soil was investigated under a FACE (Free air Carbon dioxide Enrichment) system in Yangzhou, Jiangsu, China. This experiment included two levels of atmospheric CO2 concentration and application rate of N fertilizer with the amendment of 15N-labelled wheat straw at a 0.3% ratio of straw to soil. Periodically, soil samples were collected for the analysis of straw decomposition rate, total nitrogen content, as well as 15N abundance in soil and plant. The elevated atmospheric CO2 concentration had no significant effect on the decomposition rate of wheat straw under high soil N level while significantly increased the decomposition rate under low soil N level. The elevated atmospheric CO2 concentration increased more N loss from decomposed wheat straw, especially under high soil N level, but did not affect plant N uptake of the decomposed wheat straw. Our results suggest that elevated atmospheric CO2 concentration could increase straw decomposition in N-limited soil, while result in significant N loss from the decomposed straw in N-saturated soil.