Abstract: To investigate the dynamic regulation mechanism of loading rate on crack evolution in cemented tailings backfill (CTB), uniaxial compression tests with acoustic emission (AE) monitoring were conducted at loading rates v of 0.002, 0.004, 0.008, and 0.010 mm/s. By analyzing the time-varying characteristics of AE parameters, including ring count, average frequency AF, rise time–amplitude ratio RA, and r-value (RA/AF), and applying unsupervised clustering to RA–AF datasets using Gaussian Mixture Model (GMM) combined with a moving average filter, crack types and their evolution patterns were identified. The results indicate that: ① Near peak stress, AE ring counts of CTB exhibit interval oscillations. With increasing loading rate, the fluctuation amplitude of ring counts during elastic and plastic yield stages decreases. ② As the loading rate increases from 0.002 to 0.010 mm/s, the concentrated range of AF distribution exhibited a progressive compression from 0 − 150 kHz to 0 − 100 kHz, while the RA distribution range expanded from 0 − 5 ms/V to 0 − 10 ms/V, with high-RA signals concentrated in the narrow band of AF < 80 kHz. ③ The increase in loading rate significantly affects the post-peak failure mode: the proportion of shear cracks rises sharply from 19.11% (v=0.002 mm/s) to 64.23% (0.010 mm/s), indicating a shift in failure mechanism from tensile-dominated to tensile–shear composite failure. ④ Based on stress stages, GMM clustering divides crack evolution into four phases: tensile crack dominance (0 − 20%σ_f), tensile–shear crack transition (20%σ_f − 80%σ_f), rapid shear crack growth (80%σ_f − 100%σ_f), and tensile–shear co-dominance (post-peak failure). Among them, the rapid increase in shear cracks at 80% – 100% of peak stress is identified as a precursor to localized instability. This study provides theoretical support for stability analysis and failure prediction of CTB.