The present invention provides an acceleration method for V/f controlled induction motor in flux-weakening region, which comprises: acquiring no-load magnetizing current Im of the induction motor at current stator frequency; selecting a smaller one of 0.5·Im(1/σ+1) and (Im2+σ)/(Im+σIm) as magnetizing current set point, in which σ is an estimated total leakage inductance coefficient; getting an error signal by subtracting the magnetizing current of the induction motor from the magnetizing current set point; determining the stator frequency for the next control period according to the error signal which is provided as a controlling variable of negative feedback. The acceleration method of the present invention can provide the maximum output torque in flux-weakening region and has a larger tolerance for the error of the estimated leakage inductance.