Current differential protection is an effective way to solve the protection problem of active distribution networks. The current differential protection criterion applied to transmission lines cannot be directly copied into distribution networks because of different fault characteristics. To solve this problem, the amplitude-phase relationship of fault currents in active distribution networks is analyzed first, and the restraining zone suitable for active distribution networks is given in the amplitude-phase plane. Then, a novel sector restraining zone design method is proposed to improve the protection performance. Then, considering the common current transformer (CT) saturation situation in active distribution networks, an auxiliary criterion is constructed by introducing the harmonic content ratio and fundamental frequency component amplitude ratio of the secondary currents. Finally, an overall current differential protection scheme resisting CT saturation is proposed. The simulation results based on PSCAD/EMTDC prove that, compared with conventional differential protection criteria, the scheme has higher sensitivity while ensuring reliability and it also has strong anti-CT saturation capability. This can meet the needs of active distribution networks.