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BACKGROUND: There are two influences and constraints on the observation of the structure characteristics of nano - pores in shale. Firstly, the pore size of nano - pores is blocked and buried by gold particles, which makes the planar morphological characteristics of nano - pores impossible to be observed due to the " secondary transformation" of pores. Secondly, limited by the resolution and depth of field of the instrument, the spatial ductility and other structural characteristics of nano - pores cannot be observed, so the observation of the structural characteristics of shale pore becomes a difficulty in the observation of micro - area. OBJECTIVES: The observation of the two/three dimensional structural characteristics of nano - pores in shale. METHODS: Atomic force microscopy ( AFM ) and scanning electron microscopy ( SEM) . RESULTS: The distribution of organic and inorganic pores in the black shale of Longmaxi Formation in Sichuan Basin has strong non - meanness, and the pore size and the spatial ductility of the pores are significantly positively correlated. The organic pores were distributed in a honeycomb shape, the pore size ranged from 0. lµm to 0. 4µ,m. The pores showed an obvious "integrated" feature in the three - dimensional space and had good spatial connectivity. Inorganic pores mainly develop interlayer pores of clay minerals, and the pore size is mainly distributed in the magnitude of 16 - 57nm. In addition, there are a few irregular dissolution pores in mineral grains. CONCLUSIONS: The non - meanness of pores in the 2D plane of shale leads to abrupt changes in the distribution of pores and throats, which affects the reservoir performance of the reservoir. The non - meanness of pores in shale in three - dimensional space leads to the great difference of permeability of shale reservoir in the longitudinal direction, which affects the physical characteristics of the reservoir. [ABSTRACT FROM AUTHOR]