The two were captured on a mobile phone video which shows the pair apparently at it for 45 minutes before they were stopped by police.
Two mainland Chinese students were spotted having sex in public outside of the Hong Kong Polytechnic University for an impressive 45 minutes before getting shooed off by police.
Ning Dang, 19, from Mongolia, had reportedly been celebrating his birthday at a bar close to university dorms when he met the unnamed girl.
After a boozing session to mark his birthday, the pair began walking home but only got halfway before they were filmed allegedly having sex.
Captured on a mobile phone and uploaded anonymously online, the video shows the pair apparently at it for 45 minutes before they are stopped by police.
A police spokesman said: "They were both very drunk and when officers arrived they were both fully dressed, although when the woman stood up, her trousers, which had not been put on properly, fell down."
He added:"They were both giggling but as the officers hadn’t caught them doing anything wrong they were let off with a caution."
But the video showing the girl seemingly performing a sex act on Ning and him then on top of her was later put onto social media where it went viral.
Police identified and have now arrested Ning for having sex in a public place. They are still trying to identify the young woman.
The police spokesman said: "The man says he doesn’t know the girl’s name as he only met her that night.
"We are told that she is a mainland university student aged about 20.
"It is alleged that she has returned to the capital Beijing."