Abstract: This paper presents a theoretical analysis of time-hopping pule position modulation ultra-wideband (TH-PPM-UWB) communication system under time-varying channel condition. The effect of scatters movement is analyzed under indoor channel condition with different channel parameters by simulation. Results show that the scatters movement has a slight effect on the performance of system when the input SNR is small and the effect is increasing rapidly when the SNR is increasing. On the whole, the effect of scatters movement is not greater than that of other interferences. This conclusion is similar to those from either under LOS or NLOS condition.