Abstract: The rising atmospheric CO₂ concentration affects spikelets development, grain filling process, and rice quality. However, it is unclear that whether such effects are related to grain positions on rice panicle. By using a rice FACE (Free-Air CO₂ Enrichment) platform, we grew a japoni-ca rice cultivar Wuyunjing 23, characterized with high yield and good quality, under ambient (Ambient) and elevated CO₂ concentrations (+200 μmol·mol^-1, FACE). The effects of increased CO₂ concentration on spikelet density, grain filling capacity, the appearance and eating quality of rice grains were examined and the association of such effects with grain positions on rice panicle were investigated. The results showed that CO₂ enrichment increased grain yield of Wuyunjing 23 by 18.3%. The panicle number per unit land area and filled-grain weight increased by 21.4% and 9.4%, respectively; whereas the number of spikelets per panicle and filled-grain percentage decreased by 9.0% and 2.2%, respectively. The decreased filled-grain percentage of rice grown under FACE treatment was mainly related to the increases of empty-grain percentage in all parts of rice panicle. The decrease of rice spikelets number per panicle by FACE treatment was mainly due to the substantial decrease of surviving spikelets of secondary branches in upper and middle parts of rice panicles instead of other positions. The CO₂-induced changes of filled-grain weight and filled-grain percentage were similar among grains located at different positions on rice panicle. FACE treatment reduced the green grain rate and increased the grain length and width, with the grains at different positions on rice papnicle showing similar responses. FACE significantly increased chalky grain percentage by 59% and chalkiness degree by 55%, with the increases for both parameters following the order of primary branches>secondary branches and upper part>middle part>lower part. FACE treatment slightly increased amylose content while decreased peak viscosity, hot viscosity, breakdown, final viscosity and setback, but most of these effects were nonsignificant. The gelatinization temperature of rice also reduced by 5% under FACE, and the decrease of inferior spikelets was greater than that of superior spikelets. In summary, the yield increase of Wuyunjing 23 under high CO₂ concentration was mainly related to the increases of panicle number and individual grain weight, while the panicle size was reduced. Elevated CO₂ concentration reduced green grain percentage but increased grain chalkiness, and had little effect on cooking and eating quality. The grain positions on rice panicle affected the responses of spikelets development, grain filling capacity and grain quality of rice to elevated CO₂ concentration, but the effects varied across different indices.