How to interface 8051 uart to pc.

Probably the same way as a number of thousand of other people who are doing a project with on 8051 microcontroller and who needed to interface it to a PC.

Did you check for existing reference material?

Have you searched on this site?

Have you searched on http://www.8052.com?

Have you searched on Google?

Exactly what have you done, besides asking for forum help?

Probably the same way as a number of thousand of other people who are doing a project with on 8051 microcontroller and who needed to interface it to a PC.

Did you check for existing reference material?

Have you searched on this site?

Have you searched on http://www.8052.com?

Have you searched on Google?

Exactly what have you done, besides asking for forum help?

(Just about) every evaluation board, development kit, SBC, etc has at least one UART interface that can be used to connect to a PC - so why not look at any of them for starters.

Since you're asking on the Keil forum, here are Keil's boards:
http://www.keil.com/boards/8051.asp
There are, of course, very many others to choose from...!