Based on the complex analysis problems for rotor fault diagnosis during acceleration, the method of transient frequency doubling axis trajectory analysis was proposed on the basis of the traditional axis trajectory.The Vold-Kalman order tracking method was used to extract the fault characteristic frequency and then the fault characteristic frequency was reconstructed to compound a transient frequency doubling axis trajectory changing with speed.The geometric moment method was used to extract the fault characteristics of the transient frequency doubling axis trajectory and the dimensions of such geometric moment was reduced.The relevant experiments show that by using this method, good effect has been achieved in extraction and diagnosis of the fault characteristics during acceleration of the rotor.