The invention discloses an input saturation spacecraft unwinding-free attitude tracking control method. The input saturation spacecraft unwinding-free attitude tracking control method includes the steps: calculating the error attitude according to a given command attitude and a practical attitude, then designing a control law according to a backstepping method, including designing a virtual control law and designing a feedback control law by using nonlinear damping, and finally using an extended state observer to estimate the lumped disturbance item in real time so as to obtain an attitude tracking control quantity u; and controlling the spacecraft by means of the control quantity u. The spacecraft system controlled by the input saturation spacecraft unwinding-free attitude tracking control method can track the command attitude with high precision under the condition that the moment of inertia is unknown, and the external disturbance exists, and the input is saturated. Compared with atraditional input saturation attitude control method, the input saturation spacecraft unwinding-free attitude tracking control method has anti-interference and strong robustness, and provides an effective scheme for engineering implementation of attitude tracking control.