In this research, the growth rules of pectoral of Peking duck coming from the paternal line were analyzed and the mathematical models for the growing pectoral were also estimated. In addition, direct and indirect selection responses on pectorals were further compared. Results indicated that pectoral was late maturing and logistic function was fit for describing the growth rule of the pectoral mass. The length of breastbone could be used as a marker in pectoral selection.