Hi,
I have joined a company in USA in December 1st week.
In my first pay check I see lot of tax being deducted by the company (I got some relocation bonus etc).
Since my stay in USA for 2013 is less than a month , will my tax be refunded.

Thanks in advance.

Most likely you will get a substantial refund. If you get everything back depends on the amount of your income.
When did you come exaclty to the US?

You are a non-resident alien and would file form 1040NR or 1040NR-EZ. If your earned income is less than the personal exemption (which is $3900), you will receive a refund of all your withheld income taxes. Note that social security and medicare taxes are not refunded.

You can also claim moving expenses asa non-resident alien if you qualify:
Publication 521 (2013), Moving Expenses

If you income is higher than the personal exemption/moving expenses and you were in the US 31 or more days in a row in December/November, you could wait to file your return unti lyou are a residnet alien in 2014 and then use the first year choice. Publication 519 (2012), U.S. Tax Guide for Aliens
That would make you a dual status alien for 2013: Taxation of Dual-Status Aliens
And if you are married, you can then choose to be treated as resident aliens for the entire year and file a joint return, but you would have to report worldwide income.

I would assume that filing as non-resident alien plus using moving expenses, you should be able to get a full refund

TaxForAliens has covered all pertinent issues if you are single.

If you are MARRIED, please let us know.