Abstract: The pore structure characteristics of the tidal-flat dolomite reservoirs of the fourth member of Leikoupo Formation in the Longmen Mountain front in the western Sichuan Basin were studied through core observation, casting thin films, physical property tests, capillary pressure curves and CT scanning. There are four types of reservoir:pore, fracture-pore, pore-vuggy and fracture-pore-vuggy type, which can be distinguished by displacement pressure, sorting coefficient, proportion of connected pores, coordination number and pore aspect ratio. A reservoir classification standard was established combined with reservoir space combination type. For type I reservoirs (Φ ≥ 12%), the fracture-pore type reservoir is the most favorable, while the pore type was second. For type Ⅱ reservoirs (6% ≤ Φ < 12%), the fracture-pore type and fracture-pore-vuggy type reservoirs are the most favorable, while the pore type was second. For type Ⅲ reservoirs (2% ≤ Φ < 6%), the fracture-pore type and fracture-pore-vuggy type reservoirs are favorable.