Abstract: To study the impact of corrosion on steel mechanical properties and the seismic performance of planar steel frames in the acidic atmospheric environment, 21 groups of standard steel material specimens and 4 steel frames corroded by artificial climate accelerated corrosion testing technique were tested under tensile loading and quasi-static loading, respectively. Based on the tensile test data, the linear regression relationship between the steel mechanical properties (yield strength, ultimate strength, elongation and elastic modulus) and weightlessness rate is established. Through the quasi-static test, the influence of different corrosion degrees on the seismic performance of planar steel frame (load-displacement curve, skeleton curve, strength and stiffness degradation, hysteretic energy of steel frame, etc.) are analyzed. The degradation laws of the seismic performance of the specimens under different corrosion degrees are established. The results show that corrosion has a significant impact on the seismic performance of planar steel frames. The ultimate load-bearing capacity and energy dissipation capacity decrease with the increase of the corrosion degree, while the strength and stiffness degrade and the brittle fracture is obvious.