The neutralization of fly ash concrete under loads subjected to the simultaneous attack of acid rain was investigated in this paper. And the influence of stress level and fly ash replacement on neutralization of fly ash concrete was analyzed. It was found that, the bending tensile stress accelerated the acid rain attack. The higher the stress level, the more serious the concrete corrosion. In contrast, the bending compressive stress slowed down the acid rain attack. The results also showed that the neutralization depth of fly ash concrete was increasing and concrete corrosion attacked by acid rain was more serious as the fly ash replacement increased.