The present invention relates to a metal surface salt bath nitride nitriding heat treatment method which belongs to the metal part surface heat treatment technology field. The method is performed in the following technical process: first, loading and clamping: the metal part is hung and arranged in a charging basket; second, nitriding: the metal part hung and arranged in the charging basket is positioned in a nitriding furnace, heated and charged with nitriding salt for salt bath and nitriding, and heat is preserved for 30-80 minutes in the condition that the temperature is 540-570 DEG C; third, cleaning: the nitrided metal part is cleaned, and the water temperature is controlled at 60-80 DEG C; the nitriding salt in the nitriding working process comprises carbamide, potassium chloride or barium chloride, sodium carbonate, and K 2 S, etc., according to the weight percentage, the composition of each component is respectively: 30-40 percent of carbamide, 20-28 percent of potassium chloride or barium chloride, 38-44 percent of sodium carbonate, and 0.0001-0.1 percent of K 2 S, and the sum of the weight percentage of each component is 100 percent. The present invention has the advantages of smaller deformability, short time, high efficiency, and wide application range; and also can achieve the effect of reducing the cost obviously.