Constructing unique crystal facets can increase active sites and enhance electronic structure for electrocatalysts towards the oxygen evolution reaction (OER). Here, we successfully achieved the transformation between the (311) and (222) facets of the NiFe2O4 catalysts by adjusting the ratio of Ni and Fe elements, and it was found that the activity in OER is enhanced with the exposure of (311) facet. The optimal catalyst shows a lower overpotential of 238 mV at 100 mA/cm2 current density and a small Tafel slope of 26.4 mV/dec. Furthermore, benefiting from the porous network structure, the unique super hydrophilic surface and the low-coordination Fe3+ atoms characteristic, the catalyst has an efficient mass transfer channel and fast charge transfer in the electrocatalytic OER process. More metal-O clusters were exposed on the (311) facet surface as the active site, which further improved the catalytic activity. This work presents a successful approach to creating highly active spinel catalysts through facet-engineering for electrocatalytic water splitting.