Abstract: To achieve omnidirectional seismic control in the horizontal direction and anisotropic performance modulation for metallic dampers in engineering structures, a novel Non-uniform Section Circumferential Steel Damper (NSCSD) is proposed. The damper features a chamfered rectangular configuration with non-uniform sections along its major and minor axes, enabling the precise modulation of the mechanical properties in the longitudinal and transverse directions. Initially, the analytical expressions for the yield displacement and the yield force, along with a bilinear mechanical model of the NSCSD, are established through the internal force analysis and a theoretical derivation. Numerical simulations are employed to validate the theoretical model, and parametric studies are conducted to elucidate the influence of geometric parameters on the proportional limit point, which yields adjustment coefficient ranges between the proportional limit point and the yield point (yield displacement: 1.4-1.7, yield force: 1.1-1.5). A physical prototype is designed and subjected to low-cycle reversed loading tests. The results demonstrate that the NSCSD exhibits stable and plump hysteresis loops in all directions, with errors between the experimental results and simulation and theoretical results are all below 10%, thereby verifying the reliability of the theoretical and simulation models. The findings indicate that the theoretical model proposed can rapidly determine engineering application parameters for the NSCSD and, that its anisotropic characteristics can be flexibly modulated through geometric dimensions, making it suitable for various seismic control scenarios in engineering structures.