Dear Plaban,
Thanks for contacting Top China Travel!
The airport will clean up the passengers after the last flight in and out of the airport. But the airport gate will not be closed. You can spend the night at the airport. The airport will clean up people at 11:30 pm. You are able to go to the first floor. The first floor was a bit cold, there are a lot of people picking up the plane. After the last flight arrived, there was very few people at the airport. the second floor will open at 4:00 am then you can go up.
But we are not suggesting that you spend the night at the airport mainly because it is too cold and not safe and you can’t rest well. There are hotels near the airport. We recommend you find a hotel around the airport to have a rest.
Any further request or question, please feel free to contact with us.
Sophie