The invention provides a method for casting and canceling a 10kV backup automatic switching adaptive up-grade safe and automatic device under unit connection. A main line connection way of a 110kV converting station where unit connection is combined, various constraints on 10kV backup automatic switching are comprehensively analyzed, and in-place information and the unbalance degree of the voltage of a 10kV bus serve as criteria to form a 10kV backup automatic switching casting and canceling logic matched with the up-grade safe and automatic device. The backup automatic switching equipment does not adopt single criterion, but combines voltage amplitude criterion with negative sequence voltage criterion to form the relatively perfect action logic, so the 10kV backup automatic switching can be reliably ensured to adapt to the up-grade safe and automatic device to cast and cancel, and the operation rate of the 10kV backup automatic switching equipment can be improved; all the backup automatic switching action information is from the local 110kV converting station, so remote information is not required to be acquired from an up-grade converting station; and the project applicability is high, so the building and maintenance cost of a communication channel is not required to be additionally increased.