Abstract: Reliability and precision retention are key indicators for evaluating the performance of CNC machine tools and are essential for improving their quality. To reduce the cost and duration of reliability testing, various loading devices have been developed and applied in accelerated tests. However, the lack of a framework integrating load spectrum measurement, loading device selection, and loading scheme design limits manufacturers' ability to enhance machine tool reliability and precision retention. The cutting forces of typical machining processes in a turn-milling machine are analyzed from time-domain and frequency-domain perspectives, highlighting significant differences in cutting force characteristics under different processes. The adaptability of loading devices is also discussed, and methods for selecting devices and optimizing loading schemes based on typical conditions are proposed. Finally, the limitations of current loading devices in high-frequency dynamic force loading, multi-directional coordinated loading, and bidirectional force transformation are identified. This study provides theoretical guidance for developing reliability loading schemes, contributing to the improvement of CNC machine tool testing.