Polymerization of isoprene with ternary catalyst system Fe(acac)s-electron donor (D)-Al(i-Bu)3 has been studied. It is found that the catalytic activity is related to the nature of D

and is decreased with following order: o-phenanthroline>2

2'-dipyridine> p-phenyldiami-ne> o-phenyldiamine>p-nitroaniline>o-nitroaniline. Results on 1H-NMR of polyisoprene obtained showed that content of 3

4-units in polymer reached 70%

cis-1

4 Content is about 30% but no trans-1

4 and 1

2 units were observed. X-ray

TEM and DSC studies on polymer indicated that polyisoprene shows crystalline structure

and its Tm～121℃.