Abstract: To explore the influence of the seismic capacity of the RC frame strengthened by the embedded thin-walled steel plate and the stiffener along the main force line, low-cycle reciprocating loading tests were carried out on specimens reinforced with steel plates with different height-to-thickness ratios and ABAQUS was used to establish a finite element model to analyze the effects of rib stiffness ratio, height-to-thickness ratio and axial compression ratio on the seismic performance of the reinforced specimens. Results show that there are plastic hinges at the beam end and column end of the unreinforced specimen, but only plastic hinges at the beam end of the reinforced specimens, which changed the hinge mechanism and improved the seismic performance of the specimen; stiffeners were set to thin the wall. The steel plate was divided into multiple cell grids, which enhanced the boundary constraint conditions, suppressed the out-of-plane deformation of the thin steel plate, and improved the bearing capacity and energy consumption capacity of the thin-walled steel plate. The load-bearing capacity, consumption capacity, stiffness and seismic performance of the reinforced specimens were all improved, and the beam-column joint area remaind intact during failure. However, the seismic performance of the specimens strengthened with 3 mm and 4 mm thin-walled steel plates was relatively small. The rib stiffness ratio, height-to-thickness ratio and axial compression ratio have a significant effect on the seismic performance of the specimen.