Speaking on Monday evening, Joanne Kathleen Rowling, 40, said she was well on the way to finishing the eagerly-awaited seventh Potter book.
"I wrote the final chapter in something like 1990, so I've known exactly how the series is going to end," she told a chat show on Channel 4 television.
"The final chapter is hidden away although it's now changed very slightly. One character got a reprieve. But I have to say two die that I didn't intend to die," Rowling said.
"A price has to be paid, we are dealing with pure evil here. They don't target extras, do they? They go for the main characters —— well, I do."
Asked whether one of the casualties would be Potter himself, Rowling said she had never been tempted to kill off the magician before the finale.
At the same time, she added: "I can completely understand, however, the mentality of an author who thinks, 'Well I'm gonna kill them off because that means there can be no non-author written sequels. So it will end with me and after I'm dead and gone they won't be able to bring back the character' ."
The author said she did not want to commit herself either way on Potter's fate, telling interviewers Richard Madeley and Judy Finnegan: "I don't want the hate mail, apart from anything else."
Rowling, who shot to fame from humble roots, also revealed that she still writes in cafes and based the character of Potter's good friend Hermione on a combination of herself and her sister when they were young.
As for the future after Potter, Rowling said: "I don't think I'm ever going to have anything like Harry again. You just get one like Harry."
The first six books in the series have sold more than 300 million copies worldwide and been translated into 63 languages.
The first four have also been made into blockbuster movies.
The seventh novel is reportedly due to be published next year at the earliest.
'Well I'm gonna kill them …… back the character': 这句话道出了“为什么小说作者往往让成功系列故事主人公死去”的原因：我将杀死他们（小说的主人公），这样就不会有另外的作者写续集了。小说将与我一起终结，在我死后小说人物不会再回来了。