A step-by-step simulation methodology for large-bandwidth Track-and-hold (T/H) microwave circuit is proposed. A T/H circuit is characterized accurately under the Cadence c environment. With the consideration of a specific windowing function, linearity simulation analysis could be done effectively. Moreover, the use of an input frequency generation function, in accordance with theoretical calculation, allows to treat the entire input bandwidth (BW). A simulated switched emitter follower (SEF) structure in a 0.13-µm SiGe BiCMOS technology with 24 GHz effective bandwidth and a 4 GS/s clock illustrates our methodology.