As to the formation flying with the reference satellite running on the circle orbit, the J₂ effect is analyzed. On this basis, a method is presented, which can greatly mitigate the breakage of the J₂ term by adjusting the semi-major axis of the flying-around satellite. Furthermore,the cost required for formation-keeping is evaluated under impulse assumption. Numerical results show that satellite formations with semi-major axis adjustments will last much longer, and save much more fuel.