I have a webpart with custom setting.
I add 2 property to webpart setting. I want add button to Page tab ribbon when webpart added to page and value set for the property.
It is possible that add a button to Page tab ribbon?
You can create a Ribbon Tab which shows up when your web part is selected, this is what is called a Contextual Tab.
MSDN has an article: Walkthrough: Creating a Custom Web Part with a Contextual Tab
It's a lot of work, but as Wictor Wilén writes in CKSDev version 2.0 is released - includes Contextual Web Part SPI it's been made a lot easier by CKSDev
From your question, I understand that you want to add the button to the Page Tab in the Ribbon whenever a particular WebPart is added to the page.
Here is a list of all Locations where the Button can be added: http://msdn.microsoft.com/en-us/library/bb802730
If you want to go the Server Side way, you can add the Ribbon button like this: http://sp365.co.uk/2011/09/programmatically-add-ribbon-custom-action-to-an-existing-list/
Also, I would like to mention that there is an awesome Library on Codeplex for adding ribbon buttons: http://spribbon.codeplex.com/