That's twice more than fans ordered for the Goblet of Fire.
They're now preparing for 21 June when the book comes out, and they've got to deliver hundreds of thousands of books to fans all around the country.
"There is no question it will be the biggest day in our history when we send the books out in time for June 21," a spokesman for Amazon said.
They've taken extra measures to make sure they get all the books out on time.
Harry Potter has always been huge with Amazon customers. The Chamber of Secrets DVD smashed the site's records when it sold 1,012,000 on its first day.