Abstract: In this paper, the spectral redundancy of circulation spectrum is proposed to estimate the chip interval of multi-user direct sequence-ultra wide band(DS-UWB) signal at low signal to noise ratio.The circulation spectrum density function of multi-user DS-UWB signal is derived based on the circulation spectrum density of single user,and then the spectral redundancy characteristics of signal circulation spectrum is used to estimate the chip interval.The computer simulations show that multi-user DS-UWB signal exhibits cyclostationarity,and the chip interval can be exacty estimated at rather low signal to noise ratio,and the performance is better than that of segmented correlated accumulation.