The books were brought out 10 days earlier than planned in a bid to beat so-called "pirates" who have made illegal translations of OOTP.
Hundreds of kids lined up outside China's bookshops to get their official copy of the fifth instalment in the boy wizard's adventures.
Some booksellers made sure Potter fans got their hands on OOTP as soon as possible - packing the blue-bound books into bags, so customers could get to the tills straight away.
In one city, a huge balloon was put up on a main road, saying: "Harry Potter is here. Are you?"
The Harry Potter books have now sold more than 200 million copies in 50 languages.