A novel channel estimation algorithm based on channel sparsity was proposed for TH-PPM ultra wide-band(UWB) communications.In this algorithm,the channel shortening was used to cancel the un-correct channel estimation.Then,the sparse structure property of UWB channel was used to estimate the UWB channel based on the channel estimated after channel shortening,which avoids unimportant zero taps' estimation and promotes the performance of the algorithm.Simulation results demonstrate that the new algorithm has good performance when the length of symbol is shorter than the length of channel.