The isothermal phase diagram of SiO₂-CaO-Al₂O₃ slag system was calculated by FactSage6.4. By fixing the agent MgO content at 8wt% and controlling Al₂O₃ content lower than 35wt%, a reasonable liquidus temperature and mineralogical phase of the glass slag were obtained. The effects of temperature, binary basicity w_CaO/w_SiO2 and Al₂O₃ content on viscosity of the feasible SiO₂-CaO-Al₂O₃-MgO slag were investigated by the rotating spindle method and simulating calculation. Results show that with increasing the temperature, the slag viscosity decreases, Al₂O₃ content increases from 15wt% to 35wt% and binary basicity w_CaO/w_SiO2 increases from 0.3 to 1.0 according to the univariate investigation. It is known from the smelting experiment using iron as collector that the recovery rate of palladium increases with increasing the mass fraction of waste catalyst in material system, and it increases first and then decreases with continuously increasing the basicity and temperature. With the waste Pd/Al₂O₃ catalyst used in this study and using the optimized slag ingredients of about 30wt% Al₂O₃, 8wt% MgO and binary basicity w_CaO/w_SiO2=0.5, the recovery rate of palladium reaches 99% and the residual palladium in glass tailing is less than 4.50 g/t.