The invention discloses an intervening control method for downshifting of a three-gear wire-driven automatic transmission of an electric vehicle. According to the method, a transmission electronic control unit detects a D gear on-off signal, a revolving speed signal n2 of a revolving speed transducer of a transmission output shaft, a revolving speed signal n1 of a revolving speed transducer of an electromotor and an opening signal alpha of a position transducer of an accelerator pedal, whether downshifting from a second gear to a first gear or from a third gear to the second gear is needed or not is judged, and intervening control over the revolving speed of the electromotor is conducted in all downshifting processes. Taking the downshifting from the second gear to the first gear as an example, a target revolving speed of the electromotor in downshifting from the second gear to the first gear is confirmed according to a target speed function of the electromotor in downshifting from the second gear to the first gear, the electromotor electronic control unit controls the revolving speed of the electromotor to achieve the target revolving speed of the electromotor in downshifting from the second gear to the first gear, the intervening control in the downshifting process of the wire-driven automatic transmission is conducted, and stable downshifting of the wire-driven automatic transmission is achieved.