To reveal the root cause of the sudden vibration-exceedance fault during the 150h endurance test of a certain type of turboshaft engine， the physicochemical inspection was combined with thermal-mechanical coupling simulation to carry out a full-chain mechanism analysis. The results show that severe transient thermal shocks induced by the anti-icing system’s intervention cause typical γ′-phase rafting degradation and accelerated creep elongation in DZ22 alloy blades. This excessive radial growth then triggered intense rotor-stator rubbing， generating an unbalance exceeding 60 g·cm and ultimately causing a sudden rotor vibration exceedance. Larson-Miller model calculations confirm that the extreme thermal load drastically reduces the local creep life from 150 h to approximately 80.5 h， precisely matching the actual removal timing and location. Based on these findings， a sequential control strategy of “reduce operating condition first， then activate anti-icing” was developed. Bench test results demonstrate that this strategy completely suppresses thermal overshoot at the source， eliminates the risk of rotor rubbing， and successfully ensures the safety of subsequent endurance tests for the same engine type.