The invention belongs to the technical field of catalytic and energy storage applications of high-entropy alloys, and particularly relates to a nanometer porous high-entropy alloy catalytic electrode,a preparing method thereof and applications of the electrode in bi-functional catalytic water splitting to produce hydrogen and oxygen. The electrode includes, by mole, 15-50% of Ni, 5-20% of a transition metal A, 15-50% of Mo, 5-25% of a transition metal B and 5-40% of Mn, wherein the transition metal A is Fe or Cu, and the transition metal B is one of Co, Ti or W. The alloy electrode has a porous structure, pore diameters range from 2 nm to 500 nm, and the specific surface area is 10-80 m<2>/g. The alloy electrode has advantages of 1) capability of being three-dimensional, porous, self-supporting and no need of any support or adhesive; 2) a large specific surface area and good electrical conductivity; 3) a simple material structure of the non-noble-metal porous high-entropy electrode, rich raw material sources, low prices and controllable preparation conditions; and 4) excellent catalytic performance.