The invention relates to a substation illegal line-crossing prompting method based on ultra-wideband (UWB) positioning. The method comprises: a safe area of a device is drawn in a substation three-dimensional model and a visual three-dimensional electronic fence is formed; UWB positioning system deployment is carried out in the substation; according to a content of a work ticket, a corresponding working area is drawn; a staff member in the substation wears a spatial positioning device; a background carries out calculation to obtain the real-time position of the staff member; the background carries out comparison with safety fence boundary data to calculate whether someone approaches or crosses a safety distance and a corresponding working range; if any early-warning or line-crossing behavior is made, the information is sent to a smart watch worn by the staff member; the information is sent to an administrator background; and the background records data including the person doing alarming, lasting time, and a walking path of the alarm event. Therefore, the staff member and the administrator are prompted effectively; and the background records the line-crossing behavior so as to carry out follow-up work and analysis conveniently.