On 16 Sep. 2001, Typhoon Nari (2001) landed on Taiwan. The warmer ocean temperature and unique track sustained the convection and circulation of this typhoon. The slow motion of Nari and the orographic effects brought record-breaking rainfall and caused flood in Taipei basin, taking 92 lives. The disdrometer, Integrated Sounding System, rain gauge network and dual-Doppler radar data were collected during Nari's landfall. The terrain following dual Doppler synthesis wind field showed the structure change of circulation and the topographic influence. It explained the location and duration of the heavy rain after the landfall. From the thermodynamic retrieval results, the persistent circulation of Nari after landing maintained the low pressure center, the mean radial convergence at low level provided the moisture need of the convection. The terrain blocking decided the location of rainband, which was responsible for the heavy rain in the basin area. Further study of retrieved thermodynamic fields will help to understand the mechanism of the long living convection. During the heaviest rain fall period, the disdrometer derived DSD indicated the upper limit of the drop size was about 5mm, the number of drops increased very fast and dumped heavy rainfall. From the dual Doppler synthesis, the localized horizontal convergence of the drops may explain the torrential rainfall rate. The profiler observation of ISS(Integrated sounding system) enhance the microphysical understanding in the vertical direction. Through the synthesis of radars, profiler, disdrometer and raingauge network data, the unique three dimensional structure of typhoon Nari and possible precipitation mechanisms were partially revealed.