Main indexes of rice injury by insufficient illumination (II) were selected through Gray Relation, and the effect of regulation agent on rice injured by II at different stages during heading-filling period was analyzed using Gradation Analysis and Fuzzy Comprehensive Evaluation. The results showed that the percentage of filled-grain, net assimilation rate and root activity were the top three indexes subject to injury. Application of chemical regulation agent when the injury occurred 6-20 days after heading had the best effect, with a degree of subordinacy of 0.7869.