Modern rice (Oryza sativa L.) cultivars, especially the large spikelets type rice, often fail to achieve their high yield potential due to poor grain-filling of inferior spikelets (later-flowering spikelets).By contrast to the superior spikelets(earlier-flowering spikelets), the inferior spikelets contained a lower ABA content.Application the appropriate content of ABA may promote the grain filling of inferior spikelets.However, the molecular metabolism is not classified.In this study, we performed 2-D gel-based comparative proteomic and phosphoproteomic analyses to search for differentially expressed proteins in inferior spikelets under exogenous ABA treatment.A total of 111 proteins and 31 phosphoproteins showed significant differences between ABA and CK treatments, and 100 proteins and 23 phosphoproteins were identified by MALDI-TOF/TOF MS.Further, gene expression patterns in inferior spikelets were confirmed by RT-PCR.These differentially expressed proteins act in the carbohydrate metabolism, protein metabolism, amino acid metabolism, energy metabolism, cell development,defense and secondary metabolism and photosynthesis.Our results show that ABA promotes the grain filling of inferior spikelets mainly through the regulation of these proteins and phosphoproteins.