This paper analyzes the impact of selectivity and reliability on the bus-bar protection when branch switch position is abnormal, assesses the risk of rejection or malfunction of protection device, and presents an adaptive correction method based on the principle of current vector sum of input current and output current being conservation (referred to as IO differential current). When the large differential current is balanced and only one length of bus-bar small differential IO current is imbalanced, the correction logic starts, protection device will try to add the no-position branch current into the busbar which has small IO differential current, after that if all busbars’ small IO differential current are balanced, this branch will be placed on the corrected busbar compulsively; otherwise, it will try to add to other busbar. A principle of selecting the correction and discrimination threshold of IO differential current used in modifying procedure is introduced. The feasibility of the scheme proposed is verified through simulation analysis.