Big Brother contestants were watched 24 hours per day
The broadcaster has been forced to hire more staff to deal with all the applications, which have doubled since last year's series.
However the shows bosses are keeping quiet on reports that this year's format will be radically different from previous series.
The show has been a massive hit for Channel 4, with more than seven million people tuning in to see Brian Dowling win the £70,000 first prize last summer.
The station's director of programmes, Tim Gardam, would not give details of changes to the show, but said: "It's going to be a bit different.
"We've hired extra people to wade through the applications.
"We've had to hire an extra van to bring in all the (audition) tapes. It will be a huge lottery as to who gets in."
There have been reports that the format will change - instead of just one house, there will be two, one of which will be well furnished with all the mod cons, while the other will be sparse and uncomfortable.
The contestants move between the rooms depending on how they do at challenges, say the reports.
That new format has worked well in the Netherlands, but Mr Gardam said Channel 4 was not planning to follow foreign formats.
The Dutch were the first to experience Big Brother and the format has been sold around the world.
Scrutiny
The first series in the UK was massively popular with the tabloid newspapers following the contestants every move.
Craig Phillips won the show after he helped expose fellow contestant "Nasty" Nick Bateman's underhanded tactics of trying to influence the evictions.
The shows success spawned a whole host of reality TV shows including Survivor, The Mole and Jailbreak, however in the UK none of these have come close to equalling the popularity, at least in the media, of Big Brother.
The show spawned a celebrity version in aid of charity, which was eventually won by comedian Jack Dee.
The new series will be screened during the summer.