Abstract: The optimal control problem of the attitude of a spacecraft during the stretching process of its solar array is discussed in this paper. The equations of motion for the spacecraft with solar array are obtained based on multibody system dynamics. The control problem of the attitude motion of a spacecraft with solar array can be transformed into the motion planning problem of nonholonomic system when the initial angular momentum is zero. The optimal control input signal is obtained and the optimal trajectory of a spacecraft with solar array can be obtained by using particle swarm optimization algorithm. The results of numerical simulation show that this approach is effective for the control problem of the attitude of a spacecraft during the stretching process of its solar array.