Microwave SQUID Multiplexing ( \(\mu \) MUX) is a widely used technique in the low-temperature detectors community as it offers a high capacity for reading large-scale Transition-Edge Sensor (TES) arrays. This paper proposes a Sliding Flux Ramp Demodulation (SFRD) algorithm for \(\mu \) MUX readout system. It can achieve a sampling rate in the order of MHz while maintaining a multiplexing ratio of about one thousand. Advancing of this large array readout technique makes it possible to observe scientific objects with improved time resolution and event count rate. This will be highly helpful for TES calorimeters in X-ray applications, such as X-ray astrophysics missions.