Abstract: <SPAN lang=EN-US>A compound reducing agent has been prepared to deoxidize phosphogypsum with high-sulphur coal and coal gangue as starting materials.Effects of the formula and particle size of compound reducing agent,value of</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"">&nbsp;</SPAN><SPAN lang=EN-US>n</SPAN><SPAN lang=EN-US>(C)/</SPAN><SPAN lang=EN-US>n</SPAN><SPAN lang=EN-US>(S)</SPAN><SPAN lang=EN-US>(amount-of-substance ratio of carbon and sulfur trioxide in raw material)and reaction temperature on the volume fraction of sulfur dioxide,decomposition rate of calcium sulfate in phosphogypsum,and on the desulphurization rate were studied.Results showed that all the formula and paritcle size of compound reducing agent,and reaction temperature have influences on volume fraction of sulfur dioxide.Volume fraction of sulfur dioxide could reach 16.02%,when adopting the compound reducing agent of which the mass ratio of high-sulphur coal and coal gangue was 2</SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"">∶</SPAN><SPAN lang=EN-US>1,</SPAN><SPAN lang=EN-US>n</SPAN><SPAN lang=EN-US>(C)/</SPAN><SPAN lang=EN-US>n</SPAN><SPAN lang=EN-US>(S)</SPAN><SPAN lang=EN-US> was 0.7,particle size was 111~122 </SPAN><SPAN style="FONT-FAMILY: 宋体; mso-ascii-font-family: "Times New Roman"; mso-hansi-font-family: "Times New Roman"">μ</SPAN><SPAN lang=EN-US>m and temperature was higher than 1 <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" /><st1:chmetcnv w:st="on" UnitName="℃" SourceValue="0" HasSpace="True" Negative="False" NumberType="1" TCSC="0">000 <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>.Compared with single high-sulphur coal as reducing agent,volume fraction of sulfur dioxide was increased by 1.46%.Using compound reducing agent to deoxidize phosphogypsum is propitious to reducing reaction temperature and increasing volume fraction of sulfur dioxide,decomposition rate of calcium sulfate in phosphogypsum,and desulphurization rate.It develops a new way for comprehensive utilization of high-sulhur coal and coal gangue.<BR></SPAN>