Abstract: The measurement of time difference is an important task for time difference of arrival(TDOA) localization with short baselines in RF-sensor network.The precision of TDOA is affected by frequency response of the receivers and urban electromagnetic environment.In this article the systematic error and non-line-of-sight (NLOS) error for TDOA error are analyzed, and an alike-Gaussian probabilistic model is presented based on radio wave propagation model in the urban area.Moreover, the influential factors of the model are put forward based on calibrators.A method on improving precision of TDOA is proposed and proved to be available.