This paper investigates multiuser detection technology for time hopping (TH) ultra-wideband (UWB) systems to cancel the multiple access interference (MAl) from desired signal. To reduce MAl, three interference cancellation schemes are employed: successive interference cancellation (SIC), successive interference cancellation with the maximum ratio (SIC-MR) and iterative interference cancellation with ratio threshold test (IIC-RTT). The performances of these interference cancellation schemes are compared in terms of the symbol error rate (SER) for the M-ary PPM TH-UWB systems over AWGN channel and multipath fading channel. Simulation results show that the proposed SIC-MR scheme is better than the SIC scheme. In addition, the number of stages and processing complexity are compared among three interference cancellation schemes. The IIC-RTT scheme can achieve very low complexity with acceptable performance degradation compared with the SIC scheme.