As power grid grows increasingly strong，its capacity becomes bigger and the impedance of the buses becomes smaller.When a fault strikes at the end of a long transmission line，the sensitivity of circuit breaker failure protection's voltage blocking setting could become inadequate，which will leads to the circuit breaker failure and even protection failure.A novel circuit breaker failure blocking method based on current rather than voltage-only is proposed.The new method adopts the proportion of the current of the fault line and goes to the sum of the currents of all lines connected to the bus as the tripping threshold to unblock the circuit breaker failure blocking unit.The result of RTDS simulation has proved the new method is able to thoroughly solve the problem under discussion thoroughly.