[Purposes]To obtain the impact load and the dynamic response of the shafting during the rapid engaging process of COGAG power plant, [Methods]the dynamic analysis model of the SSS clutch(Synchro-Self-Shifting Clutch) is built according to the mechanics relationship of the components on SSS clutch and dynamic simulation of the engaging process of the shafting is carried out. [Findings]Through simulation, it is found that when the damping dashpot works, a significant torque impact occurs on the clutch spiral spline and the peak of torque impact is 230.04N·m, which could result in a strong dynamic response on the shafting. In addition, it is also found that the relative position of the ratchet and pawl is random, which could cause the peak of torque impact and the dynamic response of the shafting fluctuate within a certain range. Through the experiment on plant, the correctness of the impact load calculation method and the randomness of the impact amplitude were verified, and the errors of maximum and minimum torque response amplitude were 3.56% and 8.86%, respectively. [Conclusions] Through theoretical and experimental research, this paper found that the rapid engagement of gas turbines could produce obvious torque impact and affect the safety of the power plant, which can provide a reference for the operation safety evaluation of the COGAG plant.