Developing effective and priceless electrocatalysts is an indispensable requirement for advancing the efficiency of water splitting to get clean and sustainable fuels. Herein, we reported a feasible strategy for preparing a trimetallic (NiCoFe) superior electrocatalyst with a novel open-cage/3D frame-like structure for an oxygen evolution reaction (OER). It is prepared by consequent thermal treatments of a CoFe Prussian blue analogue frame/cage-like structure under an argon (CoFeA-TT) atmosphere and then electrochemical deposition of nickel-cobalt sulfide nanosheets as a shell layer on it. The electrochemical measurements demonstrated that the deposition of NiCo-S on CoFeA-TT (NiCo-S@CoFeA-TT) has the best catalytic performance and can drive the benchmark current density of 10 mA cm-2 at a low overpotential of 268 mV with a Tafel slope of 62 mV dec-1 and an excellent long-term catalytic stability in an alkaline medium. Its outstanding electrocatalytic performances are endowed from frame/cage-like structures, highly exposed active sites, accelerated mass and electron transport, and the synergistic effect of multiple hybrid components. The NiCo-S@CoFeA-TT showed a better performance than most advanced nonprecious catalysts and the noble commercial RuO2 catalyst. This study exhibited an effective and efficient procedure to design 3D porous architecture catalysts for the energy-relevant electrocatalysis reaction.