The illusionist will then set the chamber to one he believes is safe, put the gun to his temple and pull the trigger.
He will continue to do so until he believes he has reached the bullet - and will then fire the gun at the floor.
'If I can't do it, the deal is I won't do it,' he said. 'That will be humiliating, but preferable to the alternative.'
Brown admitted his parents are unhappy about the show. 'My mum has tried to talk me out of it, but I've had to reassure her and in the end said they would just have to go with me on this one.'
He said his brother Dominic is equally unhappy and has decided to leave the country while the stunt takes place.
Derren Brown Plays Russian Roulette Live will go out at 9pm on Sunday.
A spokesman for Channel 4 said it believes that, with the warnings, the show would be responsible and it would comply with Independent Television Commission rules.