The invention relates to an on-line standby method for transformer substation secondary equipment controlled by a soft pressing plate. The on-line standby method comprises the following steps that the standby equipment receives a soft pressing plate switching command sent by a station level management module and stores soft pressing plate states; a soft pressing plate state file stored in the standby equipment is read, and the soft pressing plate states are read from the soft pressing plate state file to a pressing plate buffer zone; the soft pressing plate states stored in the standby equipment are synchronized, and whether the synchronization result is correct or not is judged; a main equipment N pressing plate and standby platform pressing plate state file after the synchronization is stored; whether the storage of the main equipment N pressing plate and standby platform pressing plate state is finished is judged; whether the standby equipment needs to switch a running state is judged; if the standby equipment needs to switch the running state, a standby equipment running state marking position is arranged, and a switching process is started; otherwise, the next step is conducted; the control process is ended. According to the on-line standby method for the transformer substation secondary equipment controlled by the soft pressing plate, on the premise that interlayer equipment is arranged to be in standby application, the number of the standby equipment is reduced, flexible switch and control of the standby function are realized, and the on-line standby method has controllability and operability.