Abstract: Digital core technology, with reliable fundamental data for the evaluation of shale oil in the first member of Qingshankou Formation in Qijia-Gulong Sag, northern Songliao Basin, supports the breakthrough of shale oil exploration in Songliao continental basin. According to the physical properties of ultra-low porosity and ultra-low permeability of shale reservoir, the digital core experiments of micro-nano CT, MAPS and QEMSCAN are used comprehensively to study the lithological characteristics, lithofacies type and pore structure of shale reservoir. The first member of Qingshankou Formation is divided into 5 lithofacies types, including low-TOC lamellar clayey limestone, low-TOC lamellar felsic limestone, medium-TOC lamellar felsic shale, medium-TOC interbedded siltstone and high-TOC lamellar siliceous shale facies. The main pore types are intergranular pore, intragranular pore and organic matter pore. Lithofacies is the main controlling factor for the development of pores and bedding fractures. The reservoir space of high-TOC lamellar siliceous shale facies is mainly composed of intragranular pores and bedding fractures, which is the sweet spot for development of shale oil in the first member of Qingshankou Formation.