The invention discloses a preparation method of a DR (dezincification resistant) copper ingot. The preparation method comprises the following steps of: adding 41-43 parts by mass of red copper raw material in a power frequency copper melting furnace and melting the red copper raw material to form molted copper; spreading 0.04-0.07 part by mass of copper alloy clear slag refining agent and evenly covering the copper melt; subsequently adding 27-30 parts by mass of wrought brass (the content of copper is 59-61%), 0.6-1.3 parts by mass of lead, 0.4-0.65 part by mass of aluminum, 0.01-0.05 part by mass of Cu-10%Mg alloy and 26-30 parts by mass of zinc ingot; after melting, horizontally stirring the molten liquid for 5-10 minutes; adding 0.6-1.2 parts by mass of Cu-20%As alloy, and horizontally stirring for 3-5 minutes after melting; pressing 0.04-0.07 part by mass of copper alloy clear slag refining agent into the melt and then continuously stirring for 10-15 minutes; by fore-furnace component analysis, adjusting the components of alloy, adding 0.01-0.015% of high-efficiency environmentally-friendly brass grain refining agent and stirring for 4-6 minutes, and then flaming; and standing, skimming slag and pouring so as to obtain the DR copper ingot. The DR copper ingot prepared by the method disclosed by the invention has good dezincification resistance and corrosion resistance capacities and simultaneously has better casting property, cutting property and easy polish-grinding property.