Based on drag-reduction requirement, references involving with relation between drag and center-of-gravity(CG) were analyzed，and theoretic minimum-drag CG position expression was summarized. On this basis, the design of target CG for Active CG Control System was discussed with the consideration of tolerances in determination of aircraft CG. At last, the control strategy for Active CG Control was addressed by taking Airbus"s A340 as an example. The results show that it is not always as good as farther backward for minimum-drag CG. The target CG should be designed based on minimum-drag CG and tolerances during CG measuring, in which fuel plays a great role .By properly designing the fuel transfer threshold, a balance between drag-reduction, fuel-economy and alleviation workload for relating system/equipment could be struck.