The embodiment of the invention provides a UWB based signal synchronization method and an indoor positioning system. The method is applied to the indoor positioning system and comprises the steps of forwarding an outdoor base station positioning signal to a first-level positioning node of each link in an indoor positioning network corresponding to the indoor positioning system by a repeater; performing preset processing on a positioning signal by the first-level positioning node of each link to obtain a corresponding synchronous positioning signal; sending the corresponding synchronous positioning signal and signal flight time to the next-level positioning node of the link by each level of the positioning node from the first-level positioning node to the reciprocal second-level positioningnode of each link; and performing clock correction on the received synchronous positioning signal based on the received signal flight time by the next-level positioning node so as to obtain a corresponding synchronous positioning signal. The UWB based signal synchronization method realizes synchronization of indoor positioning nodes and positioning signals via a wireless communication mode, simplifies the installation and maintenance process of the indoor positioning system and is convenient for adjusting the position of each positioning node.