This paper provides insight into the seismic behavior of a full-scale precast reinforced concrete wall under in-plane cyclic loading combined with out-of-plane loading replicated by sand backfill to simulate the actual condition of basement walls.The tested wall exhibited flexural cracks,owing to the high aspect ratio and considerable out-of-plane movement due to lateral pressure from the backfill.The wall performed satisfactorily by exhibiting competent seismic parameters and deformation characteristics governed by its ductile response in the nonlinear phase during the test with smaller residual drift.Numerical analysis was conducted to validate experimental findings,which complied with each other.The numerical model was used to conduct parametric studies to study the effect of backfill density and aspect ratio on seismic response of the proposed precast wall system.The in-plane capacity of walls reduced,while deformation characteristics were unaffected by the increase in backfill density.An increase in aspect ratio leads to a reduction in in-plane capacity and an increase in drift.Curves between the ratio of in-plane yield capacity and design shear load of walls are proposed for the backfill density,which may be adopted to determine the in-plane yield capacity of the basement walls based on their design shear.