Time delay estimation (TDE) lies at the heart of signal processing algorithms, however, the accuracy of conventional TDE algorithms is limited by the sampling interval. An algorithm for TDE with accuracy less than one sampling period is presented in this paper. This algorithm estimates the integral time delay (taking sampling period as a unit) by locating the maximum of Cross-correlation function (CCF), and the fractional part by calculating the slope of the straight line obtained by applying weighted fitting to the cross-spectrum phase. The weight is deduced from Best linear unbiased estimator (BLUE). Estimating the integral part first can avoid phase wrapping. The simulations show that the algorithm outperforms other algorithms for wideband signals.