Elevated CO2 levels can affect how rice grains develop and their quality. A study grew a high-yield rice variety under normal and high CO2 conditions to see how it impacted grain filling and quality. The results showed that higher CO2 levels increased grain yield by 18.3% by increasing panicle number and individual grain weight. However, it also led to fewer spikelets per panicle and lower filled-grain percentage. The decrease in filled-grain percentage was due to more empty grains in all parts of the panicle. Grain size and appearance were affected similarly across all panicle positions. High CO2 levels increased chalky grains and chalkiness degree, while slightly changing amylose content and viscosity. Overall, the increase in yield was mainly due to more panicles and heavier grains, despite some negative effects on grain quality.