Shale oil of Qingshankou Formation of Upper Cretaceous in Gulong Sag, Songliao Basin. Methods: Based on electron backscattering and secondary imaging, combined with energy spectrum analysis and thin section observation, it is found that a kind of micron pore and micron fissures formed by hydrocarbon generation and expulsion expansion in Qingshankou Formation shale in Gulong Sag. Results: The characteristics of hydrocarbon generation and expulsion high-pressure expansion micron pores are: ① generally only developed in ultra-high pressure shale oil reservoirs; ② Generally only developed in clay feldspar shale, pure clay rock is rare; ③ Most of them are nearly circular or semi-circular, with diameters ranging from 0. 5 microns to several microns, generally 1~2 microns, but up to 8 microns; ④ The wall of the hole is generally clay, and the clay on the upper edge is curved or eyebrow shaped, and the chlorite is obvious, so it is bright and eye-catching in the backscatter image; ⑤ There are many self-generated nanoscale grape-like or soybean residue clay in the hole. ⑥ high-pressure expansion micron holes for hydrocarbon generation and expulsion can be combined into four types: vertically connected to form vertical hydrocarbon expulsion chimneys; Vertically connected to form a inclined hydrocarbon exhaust chimney; The hydrocarbon exhaust pipes connected horizontally to the bedding form larger lamellar pores in the profile. Straight or slightly curved hydrocarbon exhaust chimney; 1~3 microns wide, up to 200 microns wide; High ten to twenty or thirty microns, up to 1500 microns; The top is mostly connected with the micron slit along the bedding, which is the final pressure relief and oil and gas drainage reservoir of the hydrocarbon exhaust chimney. The porosity of hydrocarbon-generating and expelling micron pores varies greatly, generally in the range of 5%~6%. The characteristics of high-pressure expansion micron fractures for hydrocarbon generation and expulsion are: ① generally only developed in ultra-high pressure shale oil reservoirs; ② Generally only developed in clay feldspar shale, pure clay rock is rare; ③ Mainly micron cracks based on foliation; ④ slightly curved tensile cracks, mostly zigzag, bypassing minerals; ⑤ Width 1-tens of microns, up to 150 micron; ⑥ Associated with pyrite, dolomite, apatite and other authigenic minerals; ⑦ It is mostly connected with hydrocarbon generation and expulsion micron pores and expulsion chimneys. In this paper, the pressure to form the hydrocarbon-generating and expandable micropores and microcracks is calculated, and the hydrocarbon-generating and expandable micropores are formed from 44.74 MPa at 1500 m to 74.81 MPa at 2500 m depth. At the same depth, the pressure of hydrocarbon expulsion is 3 MPa larger than that of hydrocarbon expulsion micropore formation. Conclusions: This is a new genetic type of micron pore and micron fracture, is a kind of effective micron pores andmicron fractures, is the most important one in Gulong shale oil reservoir. There are two main driving forces for the formation of hydrocarbon generation and expulsion expansion micron pores: one is the high-pressure expansion tension of hydrocarbon fluids; The second is the chemical dissolution power of hydrocarbon fluids. The pressure to form the micron pore and micron slit of hydrocarbon generation and expulsion is calculated. The expansion of micron pores with hydrocarbon generation and expulsion is connected with other pores to form a storage and transportation network, which greatly increases the storage capacity and permeability of the reservoir, and is the main contributor to the recoverable reserves, which is the basis and guarantee for the development of Gulong shale oil.