When I using iframe, I got salesforce header and sidebar along with visualforce page?

Use &isdtp=vw at the end of your iframe URL to not include the sidebar & header of visualforce pages.

Thanks Oliver, You have given me a simple solution 🙂

Alternatively,

<apex:page controller="myController" <b>showHeader</b>="false" <b>sidebar</b>="false" readonly="true" docType="html-5.0">

That’ll work on pages you can edit, unfortunately the page in question is part of a managed package.

Yes Oliver, Thanks Irvin for you reply, but here unfortunately we are using managed package Page.