The present invention relates to a mobile communication field. The present invention provides a method and an apparatus for WiMAX positioning by downlink preamble fast detection DPFD. The method comprises steps of: Mobile user station MSS detects downlink preambles from BSs, all of which are synchronized by in TDD mode mobile WiMAX; the TDoA of different BSs' preamble is get through preamble-based synchronization detection; and the exact location is calculated through classical TDoA algorithms. The embodiment of the present invention describes a novel concept for measuring the position of the mobile user equipment by the uplink ranging assistant downlink preamble detection. With the mobile WiMAX is accepted as a 3G standard by ITU and widely populated, the position based on WiMAX will be a market-potential service.