Abstract: The content, composition and distribution of protein in rice grain were regarded as the basis for improving the nutritional quality of rice. A varieties, Koshihikari冶, and three seed storage protein mutants from Koshihikari were used to analyze the composition and distribution of protein in grain. The result demonstrated that different distribution characteristics of protein existed between rice seed protein mutants and the wild type, Koshihikari冶, these mutants revealed various composition and content of seed storage protein in different positio of grain. These mutants can be used as basic materials to reveal the mechanism of rice storage protein accumulation and modified, and to enhance nutritional quality of rice.