Abstract: The flexural behavior of reinforced concrete beams in acid rain environment is investigated, with an aim to discover the deterioration mechanism of concrete beams servicing in acid rain environment. An artificial rainfall device was designed. Eleven reinforced concrete beams, with a cross section of 120mm×200mm, were prepared in the laboratory. Three accelerating corrosion methods, the immersion method, the dry-wet cycle method, and the artificial rainfall method, were applied to simulate real acid rain. Acid solutions with PH values of 1.5 and 2.5 were prepared by mixing sulfate and nitric acid solutions. Among the eleven beam samples, one was tested in natural conditions for comparing purposes. The remaining ten beams were tested after exposed to simulated acid environments for certain periods. Ultrasonic technology was applied to evaluate the damage depth and the compressive strength of the concrete. Dynamic tests were employed to assess the integrity of the beams. Three-point bending tests were conducted to investigate the load carrying capacity of the beams. Mechanical properties of concrete and the load carrying capacity of the beams exposed to different accelerating corrosion methods were obtained and compared. It is found that the designed artificial rainfall device is efficient to simulate real acid preipitation. It is also noted that the strength of the concrete, the natural frequency and the ultimate load of the beams, have direct influence on the damage degree of the beams.