Q:

Team Foundation server 2013 backlog order API

I need to know if any API are available to automate the backlog order. Since its cumbersome to drag and drop when PBI is very large.

A:

The rest api's for this are currently not available however you can update the "Backlog Priority" field from your application of choice. I have, in the past, used excel to bulk move items around when the backlog I large. If you have Team Explorer installed you can use the Team tab on Excel to connect to your backlog query and reorder to your hearts content.
In 2013.4 Microsoft have updated the backlog to allow a right-click "move to top" and "move to position x" to remove the need for what you are trying to do.

