To improve the seismic performance of beam-column joints of assembled steel structures,nano-metakaolin/fluororubber (NMK/FKM) composites with high damping performance were first prepared in this study by melt blending method,and then dynamic and static mechanical properties of the new material were tested at four frequencies.Taking NMK/FKM nanocom-posites as the core energy dissipation material, a simulation analysis of the right-angle viscoelastic damper proposed in this paper was performed using finite element software ABAQUS. Results show that when the frequency is 1.5 Hz, the wide damping temperature range and TA value of NMK/FKM nanocomposites reach the peak, demonstrating the best damping performance of materials. The stiffness of the right-angle viscoelastic damper increases with the displacement amplitude. The hysteretic performance of the right-angle viscoelastic damper shows nonlinear characteristics under frequencies of 0.5,1.0, and 1.5 Hz; when the frequency rises to 2.0 Hz, the hysteresis performance shows linear characteristics. The hysteresis loop area, damper stiffness, and maximum damping force gradually decrease as the thickness of viscoelastic material layers increases. The energy dissipation performance of the damper is improved as the height-span ratio increases. The dynamic response of the right-angle damper is further enhanced by adjusting the height-span ratio of dampers and the thickness of damping materials.