Phosphating slag is the hazardous waste produced during the phosphating process, which has an adverse effect on the quality of phosphating coating and phosphating cost. It is an effective method to utilize phosphating slag by extracting iron and zinc ions from phosphating slag via alkali dissolution; however, the treatment of liquid waste of residual phosphating slag is a challenge topic. In this work, the neutralization and sodium sulfide precipitation methods were used to remove the zinc from the phosphating slag waste liquid. The corresponding process conditions were optimized. And the production processes of highly purified trisodium phosphate from phosphating slag waste liquid after zinc removal were designed respectively. The removal rate of Zn2+ could reach 97.96% via neutralization precipitation method under the pH of the reaction system of 8.85, and the reaction time of 10 min, while the removal rate of Zn2+ could reach 99.80% via the sodium sulfide precipitation method under the pH of the reaction system of 6.85, the molar ratio of sodium sulfide to Zn2+ of 1:1, and the reaction time of 10 min. After adjusting the pH of the treated waste liquid to 12.30±0.03 by using 10 mol/L of NaOH solution, the phosphate anions and sodium ions were recovered by cooling and crystallization at 5℃ to produce the trisodium phosphate. The trisodium phosphate produced from waste liquid after zinc removal by neutralization precipitation method possessed the purity of 97.72% and Zn2+ content of 0.0014%, which is in line with the chemical industry standard of chemical purity. Compared with the production process of trisodium phosphate after zinc removal by using neutralization precipitation method, that using sodium sulfide precipitation method exhibited higher purity of trisodium phosphate with the value of 98.85%, and lower Zn2+ content in trisodium phosphate with the value of 0.0004%, which met the analytical purity standard of the chemical industry. The process is capable of efficiently recovering the PO43- and Na+ ions from the phosphating slag waste liquid, thereby paving a new avenue for the comprehensive utilization of phosphating slag in industry.