Abstract: In view of problems of short transmission distance, poor anti-multipath effect and low positioning accuracy existed in current underground personnel positioning technologies, an underground personnel positioning system was proposed by use of ultra wideband positioning technology based on time difference of arrival. The system sends ranging signal through multiple positioning sensors, target node carried by underground personnel receives the signal and returns it back to the positioning sensors after processing, then main positioning sensor receives ranging information sent by the positioning sensors through WiFi network and uploads it to positioning server through wired Ethernet, so as to realize real-time positioning of underground personnel, which effectively improves accuracy of underground personnel positioning.