To study the seismic performance of double steel plates and recycled concrete composite shear walls， three groups of quasi-static loading tests with varying shear-to-span ratios were designed and completed. A numerical model was established based on these experiments to investigate the impact of recycled aggregate replacement rate and concrete strength on seismic performance. The test results indicated that the buckling phenomenon predominantly took place at the bottom of the specimens for the structural steel plates， and the shear-to-span ratio emerged as a critical factor influencing the structural failure. As the shear-to-span ratio increased， the failure mode of the specimens transitioned from shear failure to flexural failure， accompanied by noticeable bolt traces on the surface of the steel plates. As the shear-to-span ratio was increased from 1 to 1.5 and 2， the ultimate load was decreased by 25.9% and 45.0%， respectively， while the displacement ductility coefficient was increased by 9.2% and 29.7%， and the equivalent viscous damping coefficient was increased by 26.0% and 89.3%. Each specimen exhibited a failure displacement angle ranging from 1/63 to 1/45， satisfying the seismic design code requirements and demonstrating excellent deformation performance. Numerical simulations demonstrated that enhancing the strength grade of recycled concrete can significantly enhance the initial lateral stiffness and ultimate bearing capacity of the specimens. Both reducing the axial compression ratio and augmenting the strength of the external steel plates can enhance the shear capacity and lateral stiffness of the specimens. By considering the synergistic effects of concrete and steel plates and aligning with the existing design codes， a composite shear wall calculation formula was proposed， incorporating an 8%~15% redundancy factor to ensure conservative and reasonable calculation outcomes.