The pore characteristics and formation mechanism of shale oil sweet spots in terrestrially saline lacustrine basins are very complex and remain a critical and challenging scientific issue in the study of terrestrial shale oil geology. To address this issue, taking the Lucaogou Formation in the Jimsar sag, Junggar basin as an example, this paper comprehensively applied the methods of rock thin section observation, XRD, high- pressure mercury injection, nitrogen adsorption, SEM, EPMA, carbon- oxygen isotope analysis and diagenetic inversion. Results show that the sweet spot of shale oil in saline lacustrine basins (as represented by the Lucaogou Formation in this study) is mainly composed of felsic minerals and carbonate minerals, with low content of clay minerals and low composition maturity. These point to the complex lithology of lacustrine mixed rock. The pores in sweet spots are mainly micro and nano pores of diverse types. Pores with radius greater than 1 μm are mainly enhanced inter- granular dissolution pores and intragranular dissolved pores, pores with radius between 100 nm and 1 μm are intercrystal pores, and pores with radius less than 100 nm are intergranular pores formed by clay- size particle. Sedimentary microfacies is the key to control the development of sweet spot pores, especially the primary pores in the beach- bar facies and delta front subfacies, which have strong compaction resistance and better preservation of intergranular pores. Dissolution is the main reason for the formation of secondary pores, which further improves the reservoir properties. The cementation of iron- bearing dolomite reduces the porosity on the whole, but also enhances the rigidity of reservoir to certain extent, which is conditionally conducive to the preservation of pores. The evolution of the pore structure of shale oil sweet spot in terrestrially saline lacustrine basins shows a “three- stage” characteristic, i.e., rapid compaction and pore reduction, pore improvement caused by acid fluid dissolution, and pore reduction by iron- bearing dolomite cementation. A good match between these three controls is the key to determine the pore evolution and final development.