Under a contract with site owners London and Continental Railways and Exel, Argent St George will carry out all the development.
Construction is due to start in 2007, after the completion of the Channel Tunnel Rail Link, terminating at St Pancras. The work is expected to continue for 15-20 years.
Argent, which worked with HBG and Carillion on the £250m Brindleyplace project in Birmingham, said its arrangement with contractors would be different for King's Cross.
Chief executive Roger Madelin said: "Because of the development and ownership structure, there will not be the pressure to package the individual developments to be design-build, fixed-price, all-risk packages.
"We will be exploring construction management routes. It doesn't mean that we won't use main contractors, but it may mean that we use them more as a management resource."