Abstract: Contributions on attitude of small satellite have mainly placed emphasize on control system, such as system design, method of control, control algorithms, mathematical model, attitude simulation and the like, but few papers have been published on the relation between attitude stabilization and mass center of small satellites. This paper analyzes effect of the displacement of mass center on attitude of small satellites from the view of structure design and dynamical balancing in light of ellipsoid of kinetic energy and motion equation. The motion equation in this paper is deduced from Lagrange equation of second kind, and represented in terms of matrix to benefit solving the equation by computer and also to make the equation concise. By the equation, the numerical simulations of attitude are carried out for a 50kg small satellite corresponding to different initial angular velocities and different displacements of mass center. The effect of displacement of mass center on stability of motion of small satellites is also analyzed. The simulations and analysis show that one or several optimal displacement of mass center exists both for attitude stabilization and stability of motion. This paper aims at providing reference for structure design, attitude control, as well as for determining the precision of dynamic balancing.