In order to improve the power supply reliability and the source acceptance capacity of distribution networks, the active ring network has become one main development trend of the distribution network. However, the connection of numerous distributed power sources will impact the power flow and fault characteristics, and thus reduce the performance of the traditional three?stage current protection scheme. In this regard, an improved current differential protection scheme is proposed for annular active distribution networks in this paper. Firstly, the expressions for the relationship between the fault currents inside and outside the annular active distribution network are derived, and thus the vectorial relationship between the fault current components at both ends can be figured out. Then the main protection criterion is constructed by the fault current ratio of the two ends of protected area section., and the auxiliary protection criterion to avoid protection misoperation is also set for the annular structure distribution network. Finally, the PSCAD/EMTDC simulation platform is used to verify the effectiveness and interference resistance of the proposed protection scheme.