Abstract: Technologic conditions for production P-Mg compound fertilizer with mixed phosphoric acid and sulfuric acid and high Mg phosphate gangue as raw materials were introduced.Influences of factors，such as sulfuric acid dosage，phosphoric acid dosage，reaction time，and reaction temperature on conversion percents of P2O5 and MgO were studied.Through single factor experiment optimum technology conditions were obtained：phosphoric acid was 110 g，sulfuric acid was 15 g，reaction time was 20 min，and reaction temperature was 50 ℃.Under the optimum conditions，conversion percent of P2O5 was more than 90% and conversion percent of MgO was over 80%.

Key words: mixed phosphoric acid and sulfuric acid, high Mg phosphate gangue, P-Mg compound fertilizer