The invention relates to a three-position signal device for a circuit breaker. The device comprises a bottom plate, a bracket and a slide plate. A three-position signal component is installed on the bottom plate on the left side of the slide plate, and a three-position signal mechanical lock is installed on the bottom plate on the right side of the slide plate. A support plate is fixedly arrangedat the upper end of the slide plate, and the right end of the support plate is connected with a positioning member in the three-position signal mechanical lock. A buckling sheet capable of horizontally rotating back and forth is arranged on the bracket, the left end of the buckling sheet is rotatably connected with the bracket, the right end of the buckling sheet is connected with an angular connecting rod in the three-position signal mechanical lock, and the front end of the buckling sheet forms a clamping protrusion. A total micro-switch is arranged on the bottom plate, and the buckling sheet horizontally moves back and forth to control the on-off of the total micro-switch. The three-position signal component in the three-position signal device for the circuit breaker can be synchronizedwith the three-position signal mechanical lock. When a screw drives the three-position signal mechanical lock at the right end via the support plate, the left end of the support plate can precisely control the three-position signal component to work to improve the operating experience of users.