The development of a low-cost and highly efficient electrocatalyst for replacing the noble metal-based materials and enhancing the efficiency of electrocatalytic generation of hydrogen is still a challenge. In this work, an amorphous FeOOH decorated CoFeAl LDH catalyst with hierarchically interconnected porous heterostructure was synthesized by a two-step method. Then, the performance of overall water splitting in alkaline solution of the prepared electrocatalyst was assessed.. Results show that by an applied current density of 100 mA·cm^-2 for the catalyst CoFeAl-FeOOH-6, the generation of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in 1 mol/L KOH solution requires only relatively low overpotentials of 298 and 193 mV, respectively. And their corresponding Tafel slopes are relatively small (i.e. 50.0 and 95.6 mV·dec^-1 for OER and HER respectively). Furthermore, the catalyst CoFeAl-FeOOH-6 as both anode and cathode in a two-electrode water splitting device can achieve excellent stability by a current density of 10 mA·cm^-2 at a cell voltage of 1.60 V. The systematical electrochemical measurement and characterization demonstrated that the enhanced electrocatalytic property of FeOOH decorated CoFeAl LDH electrode could be ascribed to the hierarchical interconnected nanosheet structure, the porous heterostructure, and the synergistic effect between them. This work could provide a promising route for promoting the electrocatalytic performance of LDH-based catalyst with a simple amorphization method, which may be expanded to other LDH materials for enhancing their electrocatalytic activities.