Tuning the surface strain of metallic nanocrystals represents a powerful strategy to engineer their catalytic properties by altering the electronic structures. However, a clear and systematic understanding of strain effect in catalytic reactions is still lacking, which restricts the use of surface strain as a tool to enhance the catalytic property of such nanocrystals. Here we use Au@Pd core-shell nanocubes and Pd nanocubes as a well-defined platform to study the strain effect in the reduction of p-nitrophenol by NaBH4. The Au@Pd core-shell nanocubes exhibited lower apparent activation energy than Pd nanocubes in the reduction of p-nitrophenol. The combination of molecular dynamic simulations and density functional theory calculations revealed that the tensile strain on Au@Pd core-shell nanocubes boosted the catalytic activity by shifting up the d-band center and thus strengthening the adsorption of pnitrophenol. (C) 2019 Elsevier Inc. All rights reserved.