In order to reduce the influence of load current on the sensitivity of current differential protection, a current differential protection based on virtual brake current is proposed. Comparing current sizes of transmission line firstly, then amplitude ratio and phase relationship of both side currents are used to construct the virtual current. The virtual current can adjust the braking size according to the current amplitude relationship on both sides of the line. Comparing to brake current using phase differences of line both side currents, virtual brake current is smaller than phase differences brake current for internal faults and it improves the sensitivity of zero current differential protection. Virtual brake current is equal to phase differences brake current for external faults and it doesn’t reduce the reliability of zero current differential protection. its adaptation is analyzed for weak feeder line and current inverse for line with series compensation device. RTDS simulation results show that virtual braking current can improve the sensitivity and reliability of the current differential protection effectively. Its adaptability is good. This work is supported by National Key Research and Development Plan of China (No. 2016YFB0900604).