Designing highly-efficient, cost-effective, and stable electrocatalysts for water splitting is essential to producing green hydrogen. In this work, a nanoflower quaternary heterostructured Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH electrocatalyst is successfully synthesized by two-step hydrothermal reactions. The sulfur in the electrocatalyst induces higher valence state metal atoms as active sites to accelerate the formation of O2. As expected, benefiting from the unique structural features and solid electronic interactions, Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH exhibits remarkable oxygen evolution reaction performance with a low overpotential of 223 mV at a current density of 100 mA cm-2, a slight Tafel slope of 65.4 mV dec-1, and outstanding stability in alkaline media. Attractively, using Ni(NO3)2(OH)4/Ni(OH)2/Ni3S2/NiFe-LDH as both a cathode and an anode, the alkaline electrolyzer delivers a current density of 10 mA cm-2 only at a cell voltage of 1.67 V, accompanied by superior durability. This work provides a facile method for the rational design of high-performance quaternary electrocatalysts.