To investigate the seismic performance of reinforced concrete (RC) beams with corroded steel bars, artificial climate accelerated corrosion tests and quasi-static loading tests were conducted on eight RC beams. The influence of corrosion level and stirrup ratio on the failure process, load-carrying capacity, deformation capacity, and energy dissipation capacity of RC beams was analyzed. Additionally, SFI-MVLEM elements and zero length section elements were used in OpenSees to simulate the flexural-shear deformation and bond-slip deformation of the beams. Model parameters were calibrated based on the principles of optimal load-carrying capacity and energy dissipation capacity. The results show that as the corrosion rate of the longitudinal bars increase from 0 to 6.8%, the shear failure characteristics of the specimens become more severe, and the load-carrying capacity, ductility, and plastic rotational capacity decrease by 6.7%, 5.1%, and 11.5% respectively. As the stirrup ratio increases, the deformation capacity, ductility, and load-bearing capacity of the specimen gradually improve. For a unit increase in longitudinal bar corrosion rate, the peak load, ductility coefficient, and plastic rotation angle of specimen DL-4 decrease by 1.48%, 1.79%, and 3.04% respectively compared to specimen DL-3 with the same stirrup ratio. Similarly, for specimen DL-8, the peak load, ductility coefficient, and plastic rotation angle decrease by 1.77%, 3.20%, and 6.97% respectively compared to specimen DL-7 with the same stirrup ratio, indicating a coupling effect between the corrosion rate and stirrup ratio parameters. The average errors in load-carrying capacity and cumulative energy dissipation capacity between simulation and testing are 8.95% and 9.82% respectively, indicating that the proposed numerical model has good accuracy and could be used for assessing the seismic performance of corroded RC beams.