Although the existence of asymmetrical profile of [ OIII ] \lambda 5007 has been discovered for ages , its filiation and physics are poorly understood .
Two new spectra of I ZWI taken on Nov 16 , 2001 and on Dec 3 , 2002 were compared with the spectra taken by BG92 .
Following results are obtained .
1 ) The certain variations of broad [ OIII ] during about 10 years separating the observations are identified .
The inferred length scale of broad [ OIII ] emitting region ranges from 0.3pc to 3pc .
By assuming a Keplerian motion in emitting region , the material emitting broad [ OIII ] is likely to be located at transient emission line region , between BLR and NLR .
2 ) We find a positive relation between the FeII emission and flux of H \beta ( or continuum ) .
On the other hand , the parameter RFe decreases with ionizing continuum marginally .
3 ) We detect a low ionized NLR in I ZWI , because of the low flux ratios { [ OIII ] _ { n } / H \beta _ { n } } ( \sim 1.7 ) .