In this study, the flexural behavior of the reinforced concrete beams attacked by acid rain environment is investigated. The objective is to discover the deterioration mechanism of the concrete beams servicing in the acid rain environment. An artificial rainfall device was designed. Eleven reinforced concrete beams, 120mm×200mm in cross-section were prepared in the laboratory. Three accelerating corrosion methods, which inclusive of immersion method, dry-wet cycle method, and artificial rainfall method, were applied to simulate the action of the real acid rain respectively. The acid solutions with pH level 1.5 and 2.5 were prepared by the mixture of sulfate and nitric acid solution respectively. One of the beams was tested in the natural condition to serve as reference; the remaining ten beams were tested after being exposed to the simulated acid environments for certain periods. Ultrasonic technology was applied to evaluate the damage depth and the compressive strength of the concrete. Dynamic test was applied to estimate the integrity of the beam. Three-point bending tests were performed to investigate the load carrying capacity of the beams. Mechanical properties of concrete and load carrying capacity of the beams exposed to different accelerated corrosion methods are obtained and compared. It is illustrated that the designed artificial device is efficient to simulate the real acid rainfall. It is shown that the strength of concrete, frequency and ultimate load of the beams, have a direct relationship to the damage degree of the beams.