The utility model discloses a switch cabinet earthing knife-switch blocking device which comprises a locking device body (5). The locking device body (5) is provided with a three-phase electromagnetic generator (1), one side of which is connected with a power supply (2) and the other side of which is connected with an earthing knife-switch (3). The three-phase electromagnetic generator (1) is linked with a baffle (4) of an operation hole of the earthing knife-switch (3). A joint lever (5) of the three-phase electromagnetic generator (1) drives the baffle (4) to move for limiting. When a cable line is charged, the three-phase electromagnetic generator (1) drives the baffle (4) to move so as to close the operation hole of the earthing knife-switch (3), and then the earthing knife-switch (3) stops working. When the cable line is not charged, the three-phase electromagnetic generator (1) drives the baffle (4) to move so as to close the operation hole of the earthing knife-switch (3), and then the earthing knife-switch (3) starts working.