The height of rice is one of the important agricultural traits, which affects on the rice architecture and production directly. The investigation of the length of the uppermost internode showed that the elongation mutation of the first internode is controlled by a recessive nuclear locus. The gene is localized between the STS marker of E30531 and the CAPS marker of C903 on the long arm of chromosome 5, apart from 6.7 cM and 2.8 cM respectively. The fine localization maps the gene between 0.3 cM flanks, which will help clone this gene and study the mechanism of the gene function.