He was rushed to hospital for emergency treatment before being transferred to Guangxi Minzu Hospital at 4am.
Doctors found that Dai's penis was at an odd angle and was so swollen it looked like an eggplant.
Dai was diagnosed with a penile fracture after tearing sponge-like erectile tissue called corpora cavernosa.
Blood flows into corpora cavernosa that runs along the penis, making it hard during an erection.
However, vigorous intercourse may tear the tissue, meaning blood bursting inside the penis causes painful swelling, according to NHS.
Dai is now recovering in hospital.
Doctors from Guangxi Minzu Hospital said penis fractures were common among men aged 20 to 40 years old, during vigorous or violent sexual intercourse.
They also warned that a fractured penis can lead to erectile dysfunction and a higher risk of complications if not treated immediately.