The invention discloses a low-tension hydroxyoximido emulsion oil-displacement polymer and a preparation method thereof. The low-tension hydroxyoximido emulsion oil-displacement polymer is composed of acrylamide, acrylic acid, water, liquid caustic soda, 2-acrylamido-2-methylpropyl sulfonic acid, methylene-bis acrylamine, potassium bromate, sodium formate, pentasodium diethylene triamine pentaacetate, chalcanthite, hydroxylamine sulfate, white oil D110, alga oleamide, Span-80, Tween-81, an emulsifying and dispersing agent OA90, azo and isohexadecyl ethylene oxide ether. The low-tension hydroxyoximido emulsion oil-displacement polymer has high molecular-weight and high solid content, is endowed with high-polymer main chain polyfunctional groups, and is an instant-dissolution reverse-phase microemulsion product with favorable stability and low tension.