Abstract: The attitude motion of solar wings on spacecraft with a flexible shaft in gravitational field is discussed in this paper. The generalized potential energy of spacecraftsystem is derived. The stability of relative equilibrium of solar wings on spacecraftwith a flexible shaft in the orbital plane is determined by use Liapunov's directmethod. Asufficient condition of stability on spacecraft is obtained, and the influence of the torsion stiffness of a flexible shaft and the mass geometry of solar wingson the attitude stability is analysed.