To evaluate the ranging performance of impulse radio ultra wideband (IR-UWB) signals, an exper-iment is performed in a typical indoor environment. In order to mitigate the ranging error caused by theoretical algorithm and practical circuits, one way-time difference of the arrival (OW-TDOA) ranging method and corre-sponding approaches are proposed and carried out according to the structure of UWB transceivers. Generalized maximum likelihood (GML) estimator based on energy detection is applied for the time of arrival estimation. The obtained results show that this UWB ranging system can achieve a relative high ranging accuracy in a multipath environment (e.g. About 5 cm at ranges up to 6 m), which is practical and meaningful for many sensor applications.