Sonu, 40, will belt out some hit numbers while Big B will jive to its beats.
"With the incomparable Sonu Nigam and the fluidity of his voice...still trying desperately to shake that b**ty," Big B posted on his blog.
Except for the third season, which was hosted by superstar Shah Rukh Khan, Amitabh has been the quiz master of the show since the beginning, but is still nervous about the premiere episode of the seventh season.
"Setting up for the opening of KBC on the Sep 6, the 7th season, and the excitement and the nervousness mounts, but giving it all that it deserves tasseled shoes and all," he posted.
The show, based on international quiz show "Who Wants To Be A Millionaire", first went on air in 2000.
I take zero credit for KBC's popularity
Megastar Amitabh Bachchan, who is set to host the seventh season of gameshow "Kaun Banega Crorepati" (KBC), says he is just a host and doesn't take any credit for the show's popularity.
"I take zero credit. The most important part of the show is the show itself. It's a very well constructed show and not just a simple question and answer thing. Very deep research has gone into it.
"Anybody can run the show. It's running in 127 countries and I am not there in those countries, I am only here in India. There is an intrinsic value in the show," Amitabh Bachchan told IANS in a group interview.
The forthcoming season will for the first time in the history of KBC will have a jackpot prize of Rs7 crores and is all set to get bigger, better and brighter.
"Season 7 will be maha crorepati and this time the prize will be Rs. 7 crores. Its back - bigger, better and brighter with format tweaks," Siddhartha Basu, CMD, Big Synergy Media Ltd, said.
The show will have few changes, including a new lifeline called Power Paplu. The money tree will now consist of 15 questions. It will also have a brand new set and design elements adding glamour to this fantastic show.
KBC will launch on Sep 6, Friday to Sunday at 8.30 pm on Sony Entertainment Television.