Taking the primary rotor blades of a highpressure compressor of a certain aero-engine as the research object, and by ways of interpretation and analysis, the kinetic equation to describe the impact of a broken blade on the rotor blades was derived, which can analytically describes the transient response of the inside broken blade's impact on the rotor blades. An example with the length, width and thickness of the rotor blade being 0.07 m, 0.03 m, 0.005m respectively was given to illustrate the transient response when one rotor blade was broken due to impact. The results show that, when the engine speed reaches up to 10000r/min, the impact point is 0.05m far from the root of the blade and the impact time is 0.02s, the maximum transient response displacement can reach up to 0.00 292 m. So, the maximum response under impulsive load should never be neglected.