Catenary geometry measurement is one of the main inspection fields to evaluate the infrastructure quality and status of power supply system on high-speed railways. Existing measurement methods have disadvantages of complex system architecture, expensive device cost, or sensitive to environment changes. In this paper, a new measurement approach is proposed which is based on infrared image processing. The system architecture is compact in hardware, and environment changes have no effects on the measurement results. Moreover, the infrared images are shared by thermal cameras from other inspection systems, which means a low device cost of the system. The proposed method has been successfully used on the comprehensive inspection train, which shows the advantages in infrastructure inspection on high-speed railways.