Designing electrocatalysts for oxygen evolution reaction with low cost, high activity and stable are crucial extremely to water splitting. Layered double hydroxides (LDHs) as a electrocatalyst exhibits a good oxygen evolution reaction (OER) performance because of its unique 2D lameller and electronic structure. However, the bulk NiFe LDHs nanosheets with large lateral size and bulk thickness hindering the exposition active sites reduce the electrocatalytic activity. To solve this problem, herein, the bulk NiFe LDHs nanosheets were successfully exfoliated into 2D ultrathin NiFe LDHs nanosheets by one-step Ar plasma. This electrocatalyst with a structure of ultrathin nanosheet and exposed more edge sites was synthesized by the Ar plasma treatment and was used to catalyze the oxidation of water. This unique structure of NiFe LDH increases the surface area and the exposure of active sites which extremely facilitate to improve the electrocatalytic performance for oxygen evolution reaction. In additions, Ar plasma also futher etched the basal planes of 2D crystals leading to production of more edge sites. Enormous studies have confirmed that positions in edge have much higher catalytic activity than positions in the basal planes. Therefore, this ultrathin NiFe LDHs nanosheets with rich edge sites as electrocatalyst showed a good OER activity with a low overpotential of 278 mV at 10 mA/cm².