He's become well known for odd stunts, like standing on a 24 metre high pole for 35 hours, and encasing himself in ice for three days.
The event, which starts on 5 September, will be shown on Sky One and Channel Four.
Some people might think he will cheat, but Blaine said: "There will be no trickery and no means of escape."
He will leave the box on 19 October.
We do not recommend hanging from a crane in a small plastic box for six weeks.