In this paper, the TH-PAM UWB system model is refined to account more completely for the structure of the blind multi-user detection (MUD) based on subspace tracking in CDMA system firstly. Then, a blind MMSE MUD algorithm is proposed. And the factors affecting the detector performance are analyzed in details by the theory analysis and computer simulations. Finally, the results demonstrate that the detector performs better than the conventional DMI detector. It can be proposed as a viable solution for high-speed indoor short range wireless communication systems.