I dropped the hd footage on dv timeline and exported it(FCP), and I see whole bunch of line in the image why? I thought when I shot in HD and then drop it to dv it will still look better then just shooting in dv.
You probably converted it to interlaced at some point.
it is normal to see interlacing lines on your pc. when you 'print to tape' does it show up on the tape version?
if it shows up then you might have the field order reversed, which you can change by right clicking the footage and choosing 'interpret footage' and changing the field order.
DV is interlaced unlike your original hvx footage.