Abstract: The current method for calculating the carrying capacity utilization rate of railway lines was difficult to meet the current needs of railway business development. Therefore, this paper adopted key technologies such as data collection and processing, data storage, and high-performance computing clusters to design a railway line carrying capacity calculation system based on distributed big data. The paper elaborated on its system architecture, system functions, etc. At present, the system has been applied in various business departments of CHINA RAILWAY. The application results show that the adopted big data computing method is more competitive in accuracy and timeliness, and can provide more scientific and accurate decision support for railway network planning and construction as well as transportation organization optimization.