A fixed-time sliding mode control approach for the deployment control issues of space tethered system (STS) is proposed in this paper, which achieves fast convergence performance under input saturation. Firstly, a fixed-time sliding mode control algorithm is designed, which guarantees the fixed-time stability of the sliding surface and the global fixed-time stability of STS. Secondly, an auxiliary system is proposed to compensate the impact of input saturation, which can be stable in fixed time too. Combining the fixed-time sliding mode control algorithm with the auxiliary system, an effective and robust controller is developed for the deployment of STS, which can achieve fixed-time convergence even in the presence of input saturation. Finally, the effectiveness of the proposed controller is demonstrated through numerical simulations.