Abstract: <SPAN lang=EN-US>MCM-22 zeolite (molecular sieve) was synthesized by dynamic hydrothermal crystallization method with polyethylene glycol 2000(PEG2000) as organic accessory ingredient and with hexamethyleneimine as template.Effect of PEG2000 on the structure,acidity and catalytic performances of MCM-22 molecular sieve has been investigated.From XRD spectrum,adding proper amount of PEG2000 while synthesizing MCM-22,better MCM-22 crystal could be obtained,but the degree of crystallinity decreased slightly.From the results of nitrogen adsorption-desorption analysis,proper amount of PEG2000 changed the distribution of the most probable pore size,which was increased to 0.587 nm from </SPAN><SPAN lang=EN-US>0.556 nm;</SPAN><SPAN lang=EN-US>additionally,the specific pore volume was increased to <?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=".59" UnitName="cm">0.59 cm</st1:chmetcnv></SPAN><SPAN lang=EN-US><SUP>3</SUP>/g from <st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue=".35" UnitName="cm">0.35 cm</st1:chmetcnv></SPAN><SPAN lang=EN-US><SUP>3</SUP>/g and BET specific surface area was increased to <st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="456" UnitName="m">456 m</st1:chmetcnv></SPAN><SPAN lang=EN-US><SUP>2</SUP>/g from <st1:chmetcnv w:st="on" TCSC="0" NumberType="1" Negative="False" HasSpace="True" SourceValue="410" UnitName="m">410 m</st1:chmetcnv></SPAN><SPAN lang=EN-US><SUP>2</SUP>/g.Acidity results tested by NH</SPAN><SPAN lang=EN-US><SUB>3</SUB>-TPD showed that by adding appropriate amount of PEG2000 the strong acid intensity was strengthened.Moreover,the synthesized molecular sieve was used as catalyst in alkylation reaction of benzene and propylene.The activity and selectivity of MCM-22 were investigated and results showed that activity of catalyst has been improved greatly,but its initial selectivity to isopropyl benzene was reduced,however,with the reaction proceeds the selectivity to isopropyl benzene increased soon. <BR></SPAN>