Potassium hydroxide (KOH) was introduced into the molybdenite roasting process to convert molybdenum (Mo) and sulfur (S) into water-soluble potassium molybdate (K₂MoO₄) and potassium sulfate (K₂SO₄). Roasting with a 1.8-fold excess of KOH at 400 °C for 3 h enabled the leaching of over 99% of Mo from the molybdenum calcine using water. A precipitation method involving potassium–magnesium (K-Mg) salts was proposed for impurity removal. Under the conditions of pH 11, 30 °C, excess coefficient of 1.7 for Mg salts, and a duration of 1 h, 98.37% of phosphorus (P) was removed from the K₂MoO₄ solution. With post-purification, over 99% of Mo crystallized upon adjustment of pH to 1. Subsequently, S and K were recovered as K₂SO₄ fertilizer from the crystalline mother liquor. An environmentally sustainable approach was proposed to conduct molybdenite production and ensure the efficient recovery of both Mo and S.