The invention relates to a flexible manometer porous metal foil electrode. The flexible manometer porous metal foil electrode comprises a flexible conductive metal layer in the middle and metal alloy layers on the two sides, and the metal alloy layers on the two sides are of a manometer porous structure. The invention further relates to a preparation method of the electrode. The preparation method includes the steps that 1, metal alloy plates with uniform structural constituents are prepared; 2, the two layers of metal alloy plates and the flexible conductive metal layer in the middle are prepared into a three-layer alloy composite plate; 3, the alloy composite plate is subjected to annealing treatment; 4, the annealed alloy composite plate is subjected to hot rolling or cold rolling; 5, the step 3 and the step 4 are repeatedly carried out till the alloy composite plate reaches a preset thickness; 6, the obtained alloy composite plate is subjected to surface grinding; 7, finish rolling is carried out till the needed thickness is reached; 8, the obtained alloy composite plate is subjected to chemical and electrochemical corrosion treatment, and the manometer porous structure is formed on the surface metal alloy layers; 9, an obtained electrode is subjected to polarization or low-temperature annealing treatment to achieve partial self-oxidation of the electrode.