Concrete deteriorated severely in the acid deposit environment. To discover the damage mechanism of the material, changes of microstructure of concrete samples exposed to the acidic solution were executed. A batch of cubic concrete samples with the dimension of 10×10×10mm3 was prepared. Acidic solution with pH level of 2.5 was deposed by the mixture of sulfuric and nitric acid solution in the laboratory. Mercury intrusion test, SEM/EDS analyses were performed on the samples exposed to the acidic solution for a certain periods. Pore structure and porosity ratio of the concrete samples were obtained. Microstructure, chemical compounds, elemental distribution in the samples exposed to the acidic solution for various periods are achieved. Development of the micro characteristics of concrete with exposure time is discussed.