Abstract: Ordovician reef beach of Tarim Basin, whicn belongs to Yijianfang and Lianglitark Formations, is mainly distributed in Tazhong, Bachu, and Lunnan areas. The lithologic characteristics are mainly binestone, bafflestone, and framestone. Yijianfang Formation features in small scale of biologic reef and its reef communities are mainly pallet spongy and alga. While Lianglitark Formation features in large scale of biologic reef and the reef communities are mainly coral stromatoporoid reefs and calcareous alga. It is the first reef ever discovered in coral-stromatopora in China. Large reef beach developed in Tazhong I slope break zone, consisting of framestone, binestone, calcirudite, and limearenite. Vertically multi-cycle knoll reefs, lime mud mound, and grain banks developed into reef flat,which is extremely thick and the highest thickness reaches more than 300meters. Geomorphologically it shows hummocky salient. Horizontally the complex is widely distributed along the slope break belt, of which the main body is located in TZ24 and TZ82 wells and it is almost 220 kilometers long from east to west. Reef beach also developed in high-quality vuggy reservoirs, as well as dissolution pores, residual intergranular pres, fissure and skeleton pore space are the main space for oil and gas accumulation. Multi-phase reef flats are vertically superposed and horizontally integrated. Tarim Basin features in well developed carbonatite slope break belt and large area favorable for exploration. Giant reef-beach oil and gas fields have been discovered in Tazhong area. Such zones as the eastern Lungu and southern Yingmaili slopes, and the Manxi slope break belt are the important areas for discoveries of reef-beach oil and gas fields.

Key words: Tarim Basin, Ordovician, Lianglitark Formation, reef beach complex, organic reef