Based on the idea of the division of the unit section with unequal length, combined with the attribute characteristics of the infrastructure in the unit section, and taking the track quality index(TQI) as the standard of the division of the unit section, a dynamic division method for unit section considering line state, infrastructure attribute and maintenance capability was proposed. The principle and priority of the division of the unit section were determined. The division of unit section was realized in two stages. The first stage was the division of unequal length and fixed unit section, which could reflect the basic situation of the line infrastructure. In the second stage, the bottom -up algorithm was employed to divide the section with unequal length dynamically, which could reflect the key sections with poor quality of the line infrastructure. By using the proposed method, the division of the unit section of Shanghai-Nanjing intercity railway infrastructure was conducted, and the results show that the method could effectively and variously divide the unit section, and the division results were close to the real state of the line.