Abstract: The Population quality and photosynthetic parameters of rice‘Xiangzhaoxian 45’of throwing transplanting under three nitrogen levels [N₁: 105 kg/hm² (low nitrogen dose); N₂: 135 kg/hm² (low nitrogen dose); N₃: 165 kg/hm² (regular nitrogen dose)] combined with 3 seedling densities [M₁: 0.27 million hills per hectare (regular seedling rate); M₂: 0.315 million hills per hectare (high seedling rate); M₃: 0.36 million hills per hectare (high seedling rate)] in a split-plot trial field were compared to verify suitable population index of high- yielding groups under seedlings- increase and nitrogen- reduction measures. The results showed that: under the premise of not affecting production, nitrogen fertilizer could reduce 18.2% when compared with current habitual amount, but the risk of reducing production would arise when nitrogen fertilizer reduced further (reduce 36.4%). Nitrogen and density had certain influence on population index of crop growth rate, net assimilation rate, leaf area index, leaf area decay rate, leaf area ratio, export rate, photosynthetic potential and grain leaf ratio etc., each population index value of N₂M₃ was in the moderate range; net photosynthetic rate, stomatal conductance, transpiration rate and water use efficiency of the highest yield combination (N₂M₃) were also at a moderate level. In summary, the population index value of high- yielding groups of early rice by throwing transplanting ought to be moderate level under seedling-increase and nitrogen-reduction measures, building suitable groups could reach high yield through reasonable collocation between nitrogen fertilizer and density, rather than increased nitrogen fertilizer blindly to pursue high- yielding, thus reduced the harm to environment on account of excessive nitrogen fertilizer application.