The spring fastener is one of the key parts of the rail track, which provides buckle pressure to keep track gauges. A high-performance spring fastener can greatly improve railway-running safety. In this investigation, on the premise of fully studying the processing process of spring fasteners, the static CCT curve of spring fasteners is determined using the thermal expansion method combined with metallographic microstructure observation and hardness test, and the post-heat-treatment process is comprehensively studied. When the tempering temperature is 460 °C, the metallographic microstructure and tests of mechanical properties well meet the technical requirements of the high-speed railway spring fastener. The studies conducted in this investigation has a valuable guiding effect on the thermal processing technology of high-speed railway spring fasteners.