Abstract: Coordinated smelting of gold and copper concentrates is one of the important technological routes for the combined extraction of copper and gold. With variations in feedstock composition, regulating the physical and chemical properties of the slag is a key measure to ensure production efficiency and increase the direct recovery rates of gold and copper. Based on the high-aluminum gold-copper concentrate of a certain copper smelting plant, this paper studied the effects of different Al₂O₃ contents and Fe/SiO₂ ratios, as well as the CaO contents in the slag, on the gold and copper contents in the slag during the smelting of gold-copper concentrate, analyzed the phase transformation rules with different CaO contents, and explored the mechanism of CaO regulation on copper slag types. The results showed that increasing Al₂O₃ content reduced the direct recovery rates of gold and copper. Modifying the copper slag with CaO effectively lowered the gold and copper contents in the slag, and increasing the mass ratio of Fe to SiO₂ reduced the required amount of CaO addition. The influence of CaO on the viscosity of slag mainly depended on the difference between the viscosity reduction due to the formation of low-melting-point phases and decreased polymerization degree, and the viscosity loss from high-melting-point phases. When the Al₂O₃ content in the slag was 9%, Fe/SiO₂ was 1.05, and the CaO content was 10%, the gold and the copper contents in the slag were reduced to 0.1 g/t and 0.42%, respectively.