How can we get to Jingtailong Hotel from beijing airport?

You must refer to the capital airport. Upon landing, you can take airport shuttle bus line 2 to Railway Station. The service hours of this line are from 24:00 to the last domestic flight arrival. So you can catch it. Then take a taxi to your hotel. It's safe eenough. The cab fare is CNY 15 to 20. Don't worry.
If you take a taxi from the airport directly, the fare is CNY 120 to 130.