Abstract: The lithological types of the first member of Yingcheng Formation of the Lower Cretaceous in Santai area consist of crypto-explosive breccia, breccia lava, welded breccias, perlite, rhyolite and tuff. Volcanic facies are volcanic conduit facies, extrusive facies, effusive facies and explosive facies. Geological evidence for determination of the position of ancient crater are lithological character，facies and distribution of perlite and rhyolite. Whole volcanic edifice can be subdivided into the central facies，the proximal facies and the distal facies. The central facies, namely as volcanic vent facies， includes volcanic conduit facies and extrusive facies. The proximal facies is effusive facies, the distal facies is explosive facies. Faciessequence is crypto-explosive breccia subfacies of volcanic conduit facies, middle subfacies of extrusive facies, inner subfacies of extrusive facies, lower subfacies of effusive facies, middle subfacies of effusive facies and pyroclastic flow deposits of explosive facies. The permeability and porosity of the proximal facies is more predominant than the central facies. The upper subfacies of effusive facies is the best reservoir.

Key words: Songliao Basin, Yingcheng Formation, ancient volcanic edifice, volcanic facies, reservoir