A latch mechanism for operation mechanism of circuit breaker, wherein the operation mechanism of circuit breaker comprises: a tripping component , a left side plate component , a right side plate component , a latch component , a half shaft component , a lever component and a main shaft component ; the tripping component , the latch component and the lever component are mounted between the left side plate component and the right side plate component , the half shaft component and the main shaft component penetrate through the left side plate component and the right side plate component and extend out of the left side plate component and the right side plate component ; the tripping component , the latch component , the half shaft component , the lever component and the main shaft component move in linkage; wherein: the tripping component comprises a tripping buckle , a latch surface is provided on a second end of the tripping buckle ; the latch component comprises a sheet metal piece rotating about a rotation shaft and a bearing mounted on the sheet metal piece ; the bearing is in contact with the latch surface, and the latch component limits the tripping component ; the half shaft component comprises a half shaft , the sheet metal piece is in contact with the half shaft , and the half shaft component limits the latch component ; characterized in that the tripping component , the latch component and the half shaft component form a two-level latch, wherein the second end of the tripping buckle is hook shaped, a second inclined surface is formed on an outer side of the hook, the second inclined surface is the latch surface, wherein when the second inclined surface of the tripping buckle is pressed and locked by the bearing , a force arm (L5) exists, a latch component spring drives the sheet metal piece to rotate about a rotation shaft with a torque generated by utilizing the force arm (L5), so that an end portion of the sheet metal piece presses the half shaft , and wherein in a process of re-closing, the bearing presses the second inclined surface of the tripping buckle and an adjacent surface of the second inclined surface , and the bearing is tangent to the second inclined surface and the adjacent surface . the tripping component comprises a tripping buckle , a latch surface is provided on a second end of the tripping buckle ; the latch component comprises a sheet metal piece rotating about a rotation shaft and a bearing mounted on the sheet metal piece ; the bearing is in contact with the latch surface, and the latch component limits the tripping component ; the half shaft component comprises a half shaft , the sheet metal piece is in contact with the half shaft , and the half shaft component limits the latch component ; characterized in that the tripping component , the latch component and the half shaft component form a two-level latch, wherein the second end of the tripping buckle is hook shaped, a second inclined surface is formed on an outer side of the hook, the second inclined surface is the latch surface, wherein when the second inclined surface of the tripping buckle is pressed and locked by the bearing , a force arm (L5) exists, a latch component spring drives the sheet metal piece to rotate about a rotation shaft with a torque generated by utilizing the force arm (L5), so that an end portion of the sheet metal piece presses the half shaft , and wherein in a process of re-closing, the bearing presses the second inclined surface of the tripping buckle and an adjacent surface of the second inclined surface , and the bearing is tangent to the second inclined surface and the adjacent surface . <EOS>