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In this research, copper smelting slag was processed under a pressurized oxygen atmosphere and low acidity conditions to achieve the selective extraction of copper and zinc and to let the iron and silicon in the slag be transformed and reconstructed into hematite and amorphous silica, respectively. The composition and the structure of the raw materials and the leaching residue were characterized by ICP-AES and XRD, and the mechanism of the selective leaching of copper and the phase reconstruction of ferrous and silicon were revealed. The results showed that under the following conditions: a sulfuric acid concentration of 0.4 mol/L, a reaction temperature of 200 °C, a liquid–solid ratio of 6 mL/g, an oxygen partial pressure of 600 kPa, a leaching time of 80 min, and a particle size of − 150 to + 74 μm, the leaching efficiencies of the Cu, Zn, Fe, and Si from copper smelting slag were > 95 wt%, > 98 wt%