If I want to build up a website to offer bitcoin exchange service, how to add my site to https://bitcoin.org/en/exchanges Does anybody give me a clue?
I want to run some business with exchange bitcoin for people. But how to make it well known? Adding it to bitcoin.org's list is a good idea, but is that possible, and how to achieve this?
You could probably open a pull request to the bitcoin.org github repository here: https://github.com/bitcoin-dot-org/bitcoin.org

Specifically, this file is the one which provides the content for the exchanges page: https://github.com/bitcoin-dot-org/bitcoin.org/blob/master/_templates/exchanges.html

Then the owners of that project can review the change and decide whether it is an appropriate addition to the website. Keep in mind that if you are just starting out a new exchange, it may not be established/trusted well enough to be featured on such a site, and that is up the site owners' discretion.