S1: mixing a low nickel matte converter slag with quicklime, then roasting to obtain a roasted material; the low nickel matte converter slag contains FeSiO₃; a mass ratio of the quicklime and the low nickel matte converter slag is (0.1-0.3):1; a temperature of the roasting is 800° C. to 1350° C.; and a time of the roasting is 0.5 h to 2.0 h;

S2 performing a grinding and a magnetic separation to the roasted material to obtain a silicate and an iron-rich slag;

S3: adding a strong alkali solution to the iron-rich slag for a leaching treatment, and performing a solid-liquid separation to obtain a filtrate and a filter residue; the strong alkali solution has a concentration of 0.1 mol/L to 4.0 mol/L; and a time of the leaching treatment is 0.5 h to 3.0 h;

S4: mixing the filter residue with an acid solution to perform an oxidative pressure acid leaching, then performing a solid-liquid separation to obtain a leaching solution and an iron oxide red; a solid-to-liquid ratio of the filter residue and the acid solution is 1 g: (0.5-5) mL; the oxidative pressure acid leaching has an oxygen partial pressure of 350 kPa to 700 kPa, a temperature of 160° C. to 225° C., and a pH of 2.0 to 3.0;

S5: introducing a hydrogen sulfide gas into the leaching solution, adjusting pH, then performing a solid-liquid separation to obtain a copper sulfide precipitate and a nickel-cobalt-containing filtrate;

wherein a mass content of nickel in the low nickel matte converter slag is 0.93 wt % to 1.38 wt %.