Abstract: As chemical and physical properties of members were changed by corrosion, the aseismic behavior of a structure was degenerated. Therefore, a mixture distribution model was derived by taking annual rainfall records in Chongqing as an object firstly. Three different corrosion modes of acid rain were proposed by combined with this mixture distribution model and metal corrosion characteristics. Then, there were 14 full-scale Q345 equal-angles and 25 material specimens were corroded by different corrosion modes and corrosion periods. Through the results of a material test, the variation law of the mechanical properties of Q345 steel was discussed, and those corresponding mathematical expressions with a corrosion damage were also proposed. At last, through a quasi-static test, the failure modes and hysteretic curves of Q345 equal-angles were obtained, and the main parameters for estimating the earthquake resistant behavior of Q345 equal-angles were also studied, such as load-carrying capacity, ductility ratio, stiffness degenerated and energy dissipation coefficients. It can be found that: 1) the mechanical property was degenerated with corrosion damages, even the yield point was disappeared. 2) the experimental and theoretical values of load-carrying capacity were all decreased with corrosion damages. However, the corrosion damage could not be calculated by the formula of current steel structural code. 3) as the cycles and area of hysteresis loops were decreased, the parameters for estimating earthquake resistant behaviors were influenced evidently by corrosion damages.