The invention relates to a preparation method of anhydrous sodium sulfide for PPS. The preparation method of anhydrous sodium sulfide for PPS can be applied to industrial production operation. According to the preparation method of anhydrous sodium sulfide for PPS, a vacuum rake type drying machine is adopted to indirectly heat materials containing materials difficult to remove like crystal water; nitrogen is used for protecting the materials in the feeding phase and the discharging phase, vacuum operation is carried out on the materials in the drying process, and therefore oxidation of the materials is avoided; in the drying process, a multi-section temperature rise (80-170 DEG C) drying method is adopted, and the materials are prevented from melting and bonding the wall of devices; in an offgas treatment phase, moisture and harmful gas are effectively processed through the washing function of a washing tower, and therefore a series of problems produced when an existing preparation method of anhydrous sodium sulfide for PPS is used are solved.