Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">Potassium dihydrogen phosphate was prepared by double decomposition reaction with calciferous wastewater in gelatin factory and potassium chloride as raw materials.Influences of reaction parameters,such as pH,reaction temperature,reaction time,liquid-solid mass ratio,and amount-of-substance ratio of potassium to phosphorus on yield of phosphorus were investigated through single factor experiment.Results showed that when pH was 8.5,precipitation rate of phosphorus was the highest;the yield of phosphorus was up to 90% and the quality of potassium dihydrogen phosphate reached agriculture grade standard when reaction temperature was <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="60" UnitName="℃">60 <SPAN lang=EN-US style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman""><SPAN lang=EN-US>℃</SPAN></SPAN></st1:chmetcnv>,reaction time was 2.5 h,liquid-solid mass ratio was 2.5,and amount-of-substance ratio of potassium to phosphorus was 1.1.</SPAN>