Abstract: Steel arch frames are widely used in the maintenance of operational railway tunnels; however, their installation still relies primarily on manual labor, which presents challenges such as high difficulty and low efficiency. To address this issue, a systematic analysis was conducted on the installation methods and process characteristics of steel arch frames in tunnel lining defect remediation. In response to technical difficulties—including short maintenance window periods, stringent requirements for procedure coordination, high risks associated with crossing overhead catenary wires due to spatial constraints, and limited working space that restricts human–machine operations—a design scheme for a steel arch frame installation machine suitable for operational railway tunnel defect remediation was proposed. The machine is capable of adjusting and correcting the position and posture of steel arch frames with six degrees of freedom, enabling mechanized installation at the tunnel crown. This significantly improves installation efficiency and ensures both construction safety and quality during defect remediation.