Abstract: Clarifying the performance degradation patterns of carbon fiber reinforced polymer (CFRP) during service is of significant engineering importance for the reliability design of lightweight critical components. This study systematically analyzes the mechanical properties and internal damage characteristics of CFRP after interrupted loading at different stress levels (435 MPa and 406 MPa) and different life ratios (25%, 50%, and 75%), through three-point bending static strength and fatigue experiments combined with quasi-in situ micro-CT observations. The fitting accuracy of four residual strength models—Hahn-Kim, Schaff-Davidson, NH, and power function degradation—to the experimental data is compared. The displacement growth rate curve indicates a three-stage degradation pattern of "fast-slow-fast" in CFRP under cyclic loading. Even under medium-to-low stress levels, the residual strength gradually decreases with an increasing number of cycles. Micro-CT images reveal that the number of internal microcracks increases with the loading life ratio, which is the main factor contributing to strength degradation. The Schaff-Davidson model, which reflects the intrinsic characteristic of CFRP’s residual strength approaching zero at failure, demonstrates the best predictive accuracy. This research is expected to provide experimental evidence and model references for the damage assessment and life prediction of CFRP components under cyclic loading.