Abstract: In order to explore the oil and gas exploration potential and controlling factors of the thick and tight Mesozoic breccia in the Xinglongtai buried hill in Liaohe depression, and guide optimization of Mesozoic exploration targets, fine reconstruction of geological data were carried out and controlling factors were analyzed on the Mesozoic reservoir according to core, debris, well logging and geochemical data. Our study indicates that: (1) 30 kinds of rocks in two types are developed in Mesozoic, Xinglongtai buried hill, of which the granitic breccia (the breccias here include granitic breccia and mixed breccia) is the best reservoir with space composed of structural fractures and dissolved pores; (2) the Mesozoic breccia reservoir is a layered fractured reservoir controlled by lithology and structure, and the overlapped zone of thick and homogeneous breccia with large faults is the favorable reservoir zone. After establishing lithology and reservoir identification charts based on the rock minerals, well logging and geochemical data, the lithology and reservoir profiles of 135 development wells were reconstructed, and reservoirs in 110 development wells were reinterpreted into classes I and II. Finally, profitable Mesozoic development was carried out by following the idea "conduct well test to define the controllable oil-bearing areas of old wells, and drill new wells to establish productivity", and 10 wells delivered industrial oil and gas flows. The Mesozoic reservoir in the Xinglongtai buried hill has been proved reserves at 108 ton scale, and in 2018, over 40 million tons of controlled petroleum geological reserves was reported.