In order to study the microscopic pore characteristics of andesite reservoir and the effect of mineral content on the andesite pore, this study takes the andesite of the Huoshiling Formation in Longfengshan of Changling fault depression, Songliao Basin as a subject. The andesite reservoir space was discerned through the observation of cores and casting thin sections. Besides, the pore size distribution of andesites and their mineral contents were quantitatively characterized by high-pressure mercury injection, nitrogen adsorption and XRD, respectively. The results show that: (1) There are various types of reservoir space in andesites, including vesicles, amygdule, intergranular pores, matrix dissolution pores and dissolution pores of amygdala, and three types of fractures including dissolution, structural and explosion fractures. (2) The pore size distribution of andesite is complex. The main pore size of andesite is mid-pore (10-20 nm) with some large-pores (>50 nm). Mid-pore and large-pore provide the main specific surface area, which are the main space for gas storage. (3) The andesite reservoir space in the study area is mainly controlled by dissolution, as supported by the relationship between the change of mineral content and porosity evolution. The porosity of andesites decreases with the increase of quartz and chlorite content, but increases with the increase of soluble mineral, e.g., feldspar content.