Current transformer saturation has always been one of the major problems of degraded reliability of the transformer differential protection. The ratio restraining differential characteristic can enable the transformer protection to be immune to the mal-operation in the external fault to some extent. But how to unblock the differential protection rapidly for the transferring fault from an external one to an internal one has become a new problem. This paper presents a new method of unblocking the differential protection for the transferring fault. In the method proposed， current comparison is made between the maximal val-ue of the integrated negative phase sequence component of the current on the two sides of a transformer and the integrated nega-tive phase sequence component of the differential current. Based on the current comparison results， the method proposed can not only accurately identify the internal fault and the external one， but also the transferring fault developed from the external fault to the internal one. Simulation results of ATP validate the effectiveness of the method proposed.