I got job in bank is it allowed for a muslim to work in banks

What country are you referring to?

Does countries that are predominantly Muslin have banks?

I am not sure for myself, never having been to any other country, however I am sure they do have banks, and I suspect most if not all the employees are Muslim.

If the OP is talking about banks where Sharia Law is observed, then interest, among other traditional banking concepts cannot be instituted. (thanks to a member PM for the clarification).

This question is being moved to the Islam category.

First you are an employee, not running the bank, and as noted this deals with the restrictions on charging interest.

The other issue is that there are many groups that make up Islam, and some are more restrictive on their beliefs than others.

Since this is a major concern or you would not have asked it, I suggest discussing this with your religious leader locally to see how they feel on the issue.