The rice varities harboring Wx-mp genotype generally results in 10% of amylose, which brings elite eating quality (e.g soft and elastic) favorited by consumers in Yangtze River Region, China. In order to identify Wx-mp carrying rice germplasm in future breeding, a functional marker associating to Wx-mp has been developed. By tests in 242 japonica rice materials collected from southern China, twenty-six germplasms were found carrying Wx-mp gene. Out of that, 25 varieties or breeding materials were collected from Jiangsu, the others from Shanghai. By validation using Sanger sequencing, this newly-developed marker proved 100% accuracy within 26 samples. Furthermore, average content of amylose was 9.2%, with a range of 3.3%. The rice cultivar Nanjing 505 with the lowest amylose content was 7.3, while cv. Nanjing 46 showed a highest amylose content of 10.6%. Thus, by deployment of the new functional marker, this study unlocked the distribution of Wx-mp carrying cultivars that were was mainly found in Jiangsu and shanghai Province.