The invention relates to a preparation process of an external oxidation dispersion strengthened copper alloy. The preparation process comprises the following steps: proportioning and smelting metallic copper and metallic aluminium, and controlling the temperature of a smelting furnace to be 1,250-1,300 DEG C; performing continuous casting on a smelted copper aluminium alloy, and controlling the temperature of cooling water of a casting crystallizer to obtain an oxygen-containing alloy copper bar; repeatedly and continuously extruding the oxygen-containing alloy copper bar in a closed extrusion cavity by use of a continuous extruder to obtain a uniform-ingredient alloy copper bar; and then performing high-temperature aging treatment, enabling sufficient replacement reaction in a protective gas to ensure generation of Al2O3, performing cold-drawing treatment to obtain a dispersion strengthened copper alloy, and eliminating unqualified products to obtain a finished Al2O3 dispersion strengthened copper alloy. The preparation process of the dispersion strengthened copper alloy is shortened in flow and low in cost, the obtained copper alloy product is stable in quality and excellent in performance, the demand of the society for the high-strength and high-conductivity dispersion strengthened copper alloy is satisfied, the preparation process can be conveniently popularized in more fields, and the economic efficiency and the practicability are high.