The paper presents an application instance of CZX-22A controlbox mal-operation from secondary circuit’s mistaken wiring, and analyzes academic reason of controlbox mal-operation in detail. Mistaken wiring leads to DC source parataxis existing in the breaker control circuit, when one route control source is broken down for some reason, it could result in controlbox mal-operation and the accidental trip. By experiment and calculation, this paper brings forward a view of preventing controlbox mal-operation, which alters components’ parameters on circuit board of controlbox, thus ensuring the reliability of relaying protection and the security of the grid.