Parameters of induction motors have crucial influence on simulation precision of a power system. This paper proposes a dynamic aggregation method of induction motors. In this method， firstly， based on the electromechanical model of induction motors， by using the coefficients of the electromechanical equation as the characteristic vector， motors are grouped with fuzzy clustering approach. Then， coefficient of the electromechanical equations of the equivalent motor is obtained by averaging that of the individual motors in the same group. Finally， parameters of equivalent motor are calculated based on the principle that the real and reactive powers of the motors remain the same before and after aggregation. Simulation results show that the proposed method can improve the precision of simulation.