The use of channel simulators to reproduce the radio wave propagation environment in the laboratory is an important means to test ultra-wideband (UWB) communication equipment. Aiming at the frequency nonstationary characteristics of UWB channels, a UWB channel model based on stationary interval superposition in frequency domain is proposed in this paper, and a hardware real-time simulation system based on software radio platform is designed. The system uses a multi-channel data parallel processing architecture to realize real-time processing of high-rate data, and introduces an iterative algorithm and a time division multiplexing structure, which not only ensures real-time generation of channel fading but also reduces hardware resource consumption. The measured results show that the simulator can simulate and output the 600 MHz ultra-wideband signal after superposition non-stationary fading in real time. The measured results show that the simulator can support the simulation of 600 MHz UWB channel fading, the channel fading spectrum is consistent with the theoretical simulation results, and the output channel impulse response is basically consistent with the measured results. The system can provide an effective means for optimization, verification and evaluation of ultra-wideband communication systems.