Over the past two years,an abnormal growth phenomenon called shrunk-grain panicle has occurred in a large area in Jiangsu Province of China. The phenomenon is described in details by figures and characters in this article. The method with a japonica rice Wuyujing 3 as the experimental material,the characteristics of grain morphology distribution and the grain weight were studied. Normal and shrunk-grain panicles were sampled from several representative areas. The length,width,and weight of the normal grains were distributed as regular,continuous,and single peaks. Plant growth typically had a right-leaning tendency. On the contrary,the distribution of the grain morphology and weight were irregular and nearly double that of the shrunk-grain panicle. The proportion of the cumulative distribution in the two kinds of peaks was closely related to the degree of shrunk-grain panicle. The article discusses the phenomenon’s symptoms,problems,and diagnosis. Over the past two years, an abnormal growth phenomena called shrunk-grain panicle has occurred in a large area in Jiangsu Province of China. The phenomenon is described in details by figures and characters in this article. The method with a japonica rice Wuyujing 3 as the experimental material, the characteristics of the grain morphology distribution and the grain weight were studied. Normal and shrunk-grain panicles were sampled from several representative areas. The length, width, and weight of the normal grains were distributed as regular, continuous, and single peaks the had a right-leaning tendency. On the contrary, the distribution of the grain morphology and weight were irregular and nearly double that of the shrunk-grain panicle. The proportion of the cumulative distribution in the two kinds of peaks was closely related to the degree of shrunk-grain panicle. The article discusses the phenomenon’s symptoms, problems, and diagnosis.