Abstract: <P class=MsoNormal><SPAN lang=EN-US>Nano-sized zinc oxide was coated with silica by using sodium silicate as raw material to inhibit its photocatalytic activity.SiO</SPAN><SPAN lang=EN-US><SUB>2</SUB>-coated zinc oxide was heat-treated,and the effect of silica on thermal stability of nano-sized zinc oxide was investigated.The prepared samples were characterized by XRD,BET,and HRTEM.The photo-stability of nano-sized zinc oxide was also evaluated.Results showed that the suitable calcination tempreture 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="600" UnitName="℃">600 <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>,and the homogeneity and densification of coating layer was improved from suitable heat treatment.Moreover,the growth of nano-sized zinc oxide grains was efflectively suppressed in the process of heat treatment.<BR></SPAN></P>