The invention relates to the field of indoor positioning and aims at solving existing problems in the prior art. The invention provides a UWB-based positioning device and a railway station children positioning method. Based on the UWB technology, the position positioning is carried out. Based on the UWB positioning system of an extensible base station, the high-precision positioning of children in a large range can be realized. Therefore, children can be effectively prevented from getting lost. The positioning system is mainly used for positioning children in a waiting room. According to the invention, a positioning label sends the positioning information to a base station unit in real time within the detection range of the base station unit. The base station unit establishes a coordinate system based on the mutual positioning of a main base station and an auxiliary base station, measures the real-time distance of the positioning label corresponding to the positioning information sent by the positioning label in communicant with the base station unit, and transmits back the obtained real-time distance information to a monitoring terminal. The monitoring terminal analyzes the positioning position of the corresponding positioning label according to the distance information uploaded by the base station unit. If the positioning position of the positioning label exceeds a threshold value range, an alarm signal is sent out.