Hadexun Oilfield is the first marine sandstone one with 100×106 t petroleum reserves in Tarim Basin. It is discovered in February 1998 and began to yield oil in August 2000. It has held the total proved petroleum reserves in-place of 82.02×106 t till the end of 2004 and estimated reserves of 28.2×106 t in 2005. The annual crude oil output reached to 2.02×106 t in 2006. The oilfield is located at a nosed rise in Hadexun belt north of the Mangar Depression in the Tarim basin. The oil reservoirs consist of main Carboniferous Donghe Sandstone Member and two thin sandstone layers within Middle Mudstone Member, which have a burial depth over 5,000 m and an amplitude below 34m. Considerable difficulties were encountered in exploration and development of the field because the main Donghe Sandstone oil reservoir is a subtle stratigraphic-anticlinal trap with a unified temperature-pressure system and an inclining oil/water interface and complicated geological conditions. Exploration and exploitation history of the oilfield, general geological characteristics of the superdeep oil reservoirs, and experience and enlightenment during exploration and development are reviewed.