<

iframe 

id

="iFrame1"

 name

="iFrame1"

 width

="100%"

 onload

="this.height=iFrame1.document.body.scrollHeight"

 frameborder

="0"

 src

="index.htm"

></

iframe

>

看到了吧，关键就在于οnlοad="this.height=iFrame1.document.body.scrollHeight"！