To understand the effect of elevated CO₂ concentration, temperature, and different weather of photosynthetically active radiation (PAR) on diurnal variation photosynthetic characteristics of rice, a paddy field experiment utilizing free air CO₂ enrichment (FACE) technology was conducted at two concentration levels of CO₂ (ambient and elevated 200μmol/mol) and two temperature regimes (ambient and elevated 1-2℃) between cloudy and sunny days, using the widely cultivated inbred Japonica rice (Oryza sativa L.) Nanjing 9108 as the test material. Diurnal variation in the photosynthetic characteristics of rice were measured every hour from 9:00 to 17:00 in the two kinds of weather. The diurnal variations in net photosynthetic rate (Pn) under each treatment followed a single-peak curve during cloudy days without a midday depression in photosynthesis, and a double-peak curve during sunny days with a midday depression. The results showed that elevated atmospheric CO₂ concentrations significantly increased rice Pn. However, elevated temperature tended to reduce Pn. Therefore, elevating atmospheric CO₂ concentration by 200μmol/mol had a greater effect on the photosynthetic characteristics of rice than elevating temperature by 1-2℃. Elevated CO₂ concentration improved rice intercellular CO₂ concentration (Ci) and inhibited transpiration rate (Tr) by an average 10.8%-22.0%. Elevated temperature nonsignificantly decreased Ci and increased Tr by an average 5.0%-13.5%. Rice Tr on sunny days was larger than on cloudy days, by an average of 9.8%-31.2%. Rice stomatal conductance (Gs) decreased significantly under elevated CO₂ concentrations and temperature. This indicated that CO₂ concentration, temperature, and PAR had a comprehensive effect on rice water use efficiency (WUE). The PAR on cloudy days was 53.3% lower than on sunny days. At the same time, the average Pn on cloudy days was lower by an average of 37.1%-72.0% than that on sunny days. Compared with ambient conditions, Pn increased under elevated CO₂ concentrations average by 21.6%-38.8% and 38.6%-58.4% in the low PAR of cloudy days and in the high PAR of sunny days, respectively. It is suggested that more attention should be focused on the effect of elevated CO₂ concentration, elevated temperature, and the downward trend of PAR on rice, which would be conducive to a more comprehensive assessment of climate change impacts on rice production.