Abstract: Grain shape is a key trait controlling the rice yield and quality, a 15-base sequence (5’-tccttcaccaagga-3’) in the boundary region of the last exon of the GW3p6 gene was mutated to a 13-base sequence (5’-agtatatatacat-3’), leading to the alterations in the intron splicing sites, which in turn made the grain shape of rice slender, thereby improving the rice quality and yield. In order to promote the application of the GW3p6 gene in rice breeding for high yield and quality, a high-efficiency and low-cost functional molecular marker of GW3p6 gene based on the melting temperature (Tm) detection was developed. By designing primers flanking the GW3p6 mutation site and utilizing the melting temperature analysis function of the QuantStudio™ 3 quantitative PCR instrument, the GW3p6 genotypes of 96 rice samples were detected. The detecting results showed that the two homozygous alleles exhibited distinct melting temperatures of 74.33℃ and 71.16℃, respectively, while the heterozygous genotype displayed two non-overlapping melting peaks, enabling accurate identification of the above three different genotypes. The development of the functional marker will promote the application of the GW3p6 gene in rice breeding.