The Yong’an basin developed on the Pre-Devonian basement, locating on the southern margin of the Cathaysian block, distributing along the Zhenghe—Dapu fault zone in NE—SW direction. Based on analyzing tectonic events, paleogeography and provenances, deep seated structures, boundary structures, and so on, the authors got the conclusions as follows: 1) during Late Paleozoic, the speed of incursion and regression of the sea was controlled by the strong and weak alternation of tectonic events in different time; and 2) the basin is characterized by developing uplift-extension structures, and it has mainly undergone phases of Variscan paralic tremendous thick deposition, Indosinian transition and Meso-Cenzoic tectonic reworking .