<p>This work aims to investigate the triaxial fatigue characteristics of rock under the influence of different stress amplitude factors. In the experiments, multistage increasing-amplitude cyclic loading was performed on the sandstone specimens. Two loading modes were designed to consider the influence mechanism of cyclic stress amplitude (including upper stress limit, lower stress limit, and amplitude increment) on the fatigue mechanical properties and fracture behavior of sandstone. The stress–strain curves, mechanical parameters, and macroscopic failure characteristics of sandstone specimens were analyzed under multistage cyclic loading considering the various cyclic stress amplitude factors. Based on the proposed stress path, the impact of stress upper limit history on the conventional triaxial mechanical behavior of sandstone specimens was evaluated, and a conceptual model was proposed. The influence mechanism of stress amplitude increment on the microfracture characteristics of sandstone specimens was further discussed through scanning electron microscopy observations. The research findings provide scientific basis for fatigue failure in deep underground engineering.</p>