Abstract: In order to investigate the effects of ozone stress on photosynthesis, dry matter production, non-structural carbohydrate and yield formation of rice, a free air ozone concentration  enrichment (FACE) experiment was conducted. A super hybrid rice cultivar Ⅱyou 084 with 3 spacing levels, low plant density (LD, 16 hills per m^-2), medium (MD, 24 hills per m^-2) and high plant density (HD, 32 hills per m^-2), was grown in the field at current and elevated ozone concentrations (current×1.5). The results were as follows: Elevated ozone significantly reduced leaf SPAD value of Ⅱyou 084 by 6%, 11% and 13%, at 63, 77, and 86 days after transplanting, respectively. The declines in leaf net photosynthetic rate, stomatal conductance and transpiration rate at filling stage increased significantly on ozone stress over time. Ozone stress decreased dry matter production of rice by 46% from heading stage to plant maturity, thus reduced biomass yield by 25%. Elevated ozone decreased the concentration and accumulation of soluble carbohydrate and starch in stem of Ⅱyou 084 at jointing, heading and plant maturity, but significantly increased the dry matter transportation rate. No significant interaction was observed between ozone and planting density for photosynthesis, dry matter production and nonstructural carbohydrate of rice. The above results indicated that elevated ozone reduced photosynthesis and growth of rice Ⅱyou 084 at late growth stage, which had no relationship with planting density.