Optimizing the microstructure of a catalyst layer is considered a breakthrough to improve the electrocatalytic performance of nanomaterials. This study reports that nickel/iron layered double hydroxide (NiFe-LDH) with constant tensile strain can be achieved by flash nanoprecipitation. To control the strain extent of NiFe-LDH, a multi-inlet vortex mixer (MIVM) is employed to create a continuous adjustable shear stress field. We utilize this method to produce NiFe-LDH with a precise control over the orientation stretching along the (116) plane from 0.042% up to 0.552% by tuning the flow velocities of 55-70 mL/min. The as-prepared NiFe-LDH with aforementioned strain regulation improves their adsorption properties of oxygen on the surface and exhibits excellent oxygen evolution reaction (OER) activity modulations. There is a degressive trend along the strain degree in the tested OER performance, and a 10 mV decrease in overpotential is clearly visible, which can lead to a low overpotential of 320 mV. Furthermore, density functional theory calculations offer valuable insights into the effect of strain in the (116) plane on the adsorption of oxygenated intermediates for OER kinetics. This work which was accomplished with MIVM confirms an effective "bottom-up" strategy to regulate the structural and electronical properties of nanomaterials and is expected to enrich design principles to enhance the electrocatalytic performance.