Spacecraft formation flying is essential for space-based interferometry missions detecting gravitational waves, such as LISA, DECIGO, and the upcoming Japanese SILVIA mission. These missions require strict requirements of relative positions between spacecraft to guarantee accurate measurements. This thesis focuses on trajectory tracking for three spacecraft orbiting a General Circular Orbit (GCO). The goal is to maintain accurate relative distances despite initial perturbations and external disturbances, including J2 force perturbation and drag force. Three nonlinear control strategies are investigated: Passivity-Based Control (PD), First-Order Sliding Mode Control (FOSM), and Boundary Layer First-Order Sliding Mode Control (BLFOSM). Numerical simulations evaluate each method under realistic conditions.