Abstract: The state equation based on the Lawden’s equations is established and control method for satellite formation keeping is investigated using Linear Quadratic Regulators (LQR). Firstly, the relative disturbing forces are expressed while considering the perturbation and atmospheric drag as two major disturbing forces in low earth orbit. Then, by choosing the control weighted matrix R reasonably, the constrained optimization problem as formation keeping with electric rocket propellant can be transformed into the unconstrained optimization to be solved. The simulations show that this control method is effective.