"connect USB Flash drive (for ex. Memory bird) to 8051 family controller"

I hesitate ever to say that a thing can't be done, but I think this must be one?!

A USB Flash drive is a peripheral on the bus; therefore your poor little 8051 would have to implement a full USB host controller - a serious undertaking indeed!!

Take a look at this thread:
http://www.8052.com/forum/read.phtml?id=42520

As Michael said, you'd be far better off with a direct interface

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