In order to improve the reliability of the bridge differential protection for the DC converter, prevent the misoperation of the protection during short-circuit fault and the inrush current, the countermeasure for the CT saturation of the YD converter transformer of the bridge differential protection is proposed. The theoretical analysis and the simulation test disclose that the CT saturation in the delta winding of the YD converter transformer during the disturbance of the AC system will cause the false operation current, resulting in the misoperation. To solve this problem, the paper proposes a countermeasure that introducing the zero-sequence circulating current as the restraint current of the bridge differential protection. The time difference between the increase of the zero-sequence circulating current and the rise of the bridge differential current is utilized to determine whether to apply the proposed countermeasure. The simulation tests indicate that this countermeasure can improve the reliability of the bridge differential protection during the disturbance in the AC system, and meanwhile would not affect the sensitivity and the speed of the bridge differential protection for the internal fault.