how do dump hex file into 8051 using keil

No - it has nothing to do with the Compiler.

It is the uVision IDE that proivides the option.

But, what uVision provides is just an interface that allows you to call some 3rd-party tool.

So, what you need is some tool - with a command-line interface - that will load a hex file into whatever target you have.

Once you have got that tool working from its command line, you just have to configure the corresponding settings into uVision - as described in the Manual:

http://www.keil.com/support/man/docs/uv3/uv3_flash_programming.htm

See also: http://www.keil.com/appnotes/docs/apnt_159.asp
The details will almost certainly be different for your particular target, but the principles remain the same - including the use of the Key Sequences...

No - it has nothing to do with the Compiler.

It is the uVision IDE that proivides the option.

But, what uVision provides is just an interface that allows you to call some 3rd-party tool.

So, what you need is some tool - with a command-line interface - that will load a hex file into whatever target you have.

Once you have got that tool working from its command line, you just have to configure the corresponding settings into uVision - as described in the Manual:

http://www.keil.com/support/man/docs/uv3/uv3_flash_programming.htm

See also: http://www.keil.com/appnotes/docs/apnt_159.asp
The details will almost certainly be different for your particular target, but the principles remain the same - including the use of the Key Sequences...

Once you have got that tool working from its command line
before you try to download from uVision, make the tool you choose (USB/JTAG/RS-232-SPI - whatever matches your situation and chip) write the program to your board.

Trying to integrate before you have the tool working as a standalone is sheer folly.

Erik