Ultra-strong nanolayered metallic composites with normal coherent and in-coherent interfaces are usually subjected to severe shear instability (strain localization) due to the high density of heterogeneous interfaces. Here we show by systematic molecular dynamics simulations that the shear instability can be significantly suppressed by the addition of the amorphous interfacial layers with composition gradient in a Cu/Nb nanolayered composite. The tensile simulations show that the normal sample shows strong strain localization due to the in-homogeneous deformation among the constituent grains in the layers. The introduction of the gradient amorphous interfacial layers renders a superior strain delocalization capability in the composites through the stimulation of nano-twinning in the copper layers and the suppression of the twin boundary migration in the niobium layers. Moreover, the strength of the gradient sample is also increased due to the enhanced strain delocalization. This work provides a feasible route to enhance the strength and ductility of the nanolayered composites by architecting a composition gradient in the heterogeneous interfaces.