Abstract: The concept and the definition of the reference orbital elements are introduced using spherical geometry. In terms of the reference orbital elements, governing equations for relative motion are formulated. Under the assumption of null eccentricity of the leader satellite, as well as the small relative inclination angle in formation flight, the equations of relative motion are simplified considerably and the characteristics of relative motion are extracted. The utility of the present formulation is exemplified by constructing the formation flight of one leader and six follower satellites, which carry the synthetic-aperture reconnaissance mission in the geosynchronous orbit. The formation parameters and the orbital elements of the leader satellite are obtained to meet the application demands. The orbital elements of six follower satellites are also identified using the relative motion equations. The simulation results show that simplified equations are reasonably accurate and are suitable for orbit design of formation flight.