The invention relates to an isolating circuit breaker locking device which is installed in a circuit breaker control box and is characterized in that it comprises a substrate, a drive motor, a control motor, a drive shaft, a limit sleeve, a sleeve guide base and a limit switch; when a ground knife switch is switched off, the drive motor operates and driven a bevel gear to rotate to drive a bevel gear b, the bevel gear b rotates to drive the drive shaft to rotate; the external threads on the drive shaft drive the limit sleeve to move in the horizontal direction when rotating so that the end portion of the limit sleeve is moved to a limit sheet on a breaker lever and is abutted against the sheet; the stroke control lever connected to the limit sleeve is moved to moving the limit switch to trigger the limit switch so that the drive motor stops operating; it may also enable the limit sleeve to cooperate with the limit sheet on the circuit breaker control lever by turning off the drive motor controller and manually rotating the drive shaft.