A study of depositional characteristics is very important for petroleum geology exploration. For a long time, due to their deeply-buried, geological-complicated and bad-natural conditions etc, a study related to petroleum geology, because of poor exploration for oil and gas of Permo-Carboniferous formation from Yingen-Ejinaqi, was seldom done. Due to their deeply- buried, strongly-deformed and little of deeply-explored data, author, in purse of exploring oil and gas conditions of Permo-Carboniferous, researches into the depositional characteristics of Permo-Carboniferous formation by making full use of the outcrops from the study area and surveying in detail almost 30 sections of them. This paper shows that Permo-Carboniferous formation comprise the mudstones, volcanic rocks (or pyroclastic rocks), carbonate rocks, sandstones and conglomerates etc., accompanied by rich marine organism. The dark dominated mudstones of the formationg are potential source rocks and cap rocks. The ubiquitous volcanic rocks (or pyroclastic rocks) by which the Permo-Carboniferous formation is characterized, carbonate rocks of lenticular and prevalently-silicated, and fewer of sandstones and conglomerates make up the main reservoirs of the Permo-Carboniferous respectively. The composition and occurrence of the formations reveal that frequently-rifting and strongly-volcanism concurred in the study area through the Permo-Carboniferous age, the area, which were far from land, deep and quiet in water, are favorable to development of source rocks. The Permo-Carboniferous formation in the area includes 6 facies as follows: neritic shelf, open coast, carbonate platform, braided delta and fan delta etc. Among them, both neritic shelf and barrier coast form the source rocks and cap rocks, other facies else make up reservoirs for oil and gas respectively.