This paper proposes a novel hyperchaotic PN (pseudo-noise) sequence, which is generated by a novel Rossler hyperchaotic system. Its correlation characteristics are analyzed via numerical simulations. Then the PN sequence is applied to the direct sequence ultra-wideband (DS-UWB) system to enhance its antinoise performance. The model of chaos-based DS-UWB communication system is established in the purpose of analyzing the performance of its reception. Using the hyperchaotic PN sequence as spread spectrum address code and assuming ideal synchronization at the receivers, the bit error rate (BER) of multi-user DS-UWB system in additive Gaussian white noise(AGWN) channel is derived in terms of the noisy intensity and the number of users. Simulation results show that the hyperchaotic sequence is a PN sequence of good performance and more excellent than the chaotic sequence.