The talkshow host will book up to 50 guests and performers for the charity project in March, according to The Sun.
The show will reportedly take up BBC Three's entire schedule from 7pm until 2am.
It will also take on his usual Friday night show format, with guests being brought in and out all evening. Producers are also planning several surprises and twists.
David Walliams, Doctor Who's Matt Smith and Miranda Hart are among the stars named as possible guests.
A source said: "This will be the most exhausting thing Graham has ever done.
"Seven hours of live telly is no mean feat so Graham is booking people he knows will lift his spirits.
"There will be all the usual banter and silly clips and there will be some big set pieces too, which are being thrashed out now."
The project follows the marathon BBC Radio 1 broadcast by Chris Moyles and Dave Vitty in 2011, when they remained on air for over 50 hours.
David Walliams also completed a 24-hour quiz show marathon in 2011.