The invention belongs to the field of molecular biological techniques and molecular marker techniques, and particularly relates to a molecular marker on a pig chromosome No.7 related to the duroc pigdaily weight gain property and application of the molecular marker. An SNP site of the molecular marker on the pig chromosome No.7 related to the duroc pig daily weight gain property corresponds to the A>C mutation at the 27045611th-bp site on the international pig reference genome 11.1 version chromosome No.7, the molecular marker is obtained through whole-genome correlation analysis, the averagedaily weight gain property of 30-100 kg of a pig is obviously affected by the molecular marker. The invention further provides a primer pair for authenticating the molecular marker. By means of the molecular marker and the primer pair, the efficient and accurate molecular marker assisted breeding technology can be established; by applying the technology to the pig daily weight gain property genetic improvement, the daily weight gain of the pig is improved, enterprise benefits are improved, and core competitiveness is improved.