Compared with traditional AC power grid, the fault characteristics of the AC/DC hybrid power grid are more complex and variable. Hence there is a problem of incorrect action for the fault detection elements used in traditional AC power grid which comes up when an outgoing line fault occurs on the AC transmission line in the vicinity of the inverter station. To distinguish the fault direction under the aforementioned situation, a directional protection scheme based on the characteristics of the AC filter is proposed in this paper. Considering the information can be measured by AC line relay, a method for estimating the current provided by the AC filter is given during an outgoing line fault. According to the difference of current characteristics between forward and reverse fault, the fault direction can be judged based on waveform similarity among the currents provided by the AC filter and measured by the AC line relay. Finally, a simulation model is built on the PSCAD/EMTDC platform for extensive performance evaluation. The reliability and effectiveness of the protection scheme are verified under different cases.