【Purposes】 In-depth research on electrode materials and preparation processes to develop new electrochemical sensors for heavy metal ion detection is of great importance. 【Methods】 The porous NiCo2O4 array grown on Ni foam (NiCo2O4/NF) was synthesized by hydrothermal method. Then, the composition, morphology, and electrochemical properties of the sample were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. 【Findings】 The results show that the NiCo2O4 array is uniformly loaded on the skeleton of Ni foam with a highly open nanowire array structure. The NiCo2O4/NF composite material is directly applied as the electrode for electrochemical determination of Hg2+ solutions with different concentrations. In 0.125~2.5 μmol/L and 2.5~35 μmol/L concentration range, the detection sensitivities are 0.025 and 0.003 4 μA/μmol/L, respectively. Meanwhile, the electrode shows good stability and reproducibility. In addition, when the composite electrode is also used to detect mixed heavy metal ion solutions of different concentrations, it also shows high sensitivity and discrimination. 【Conclusions】 The research results in this paper provid a new method for designing and synthesizing high-performance electrode materials, for conveniently detecting heavy metal ions by electrochemical method.