ISG has signed up Wring to deliver site clearance after planning permission was granted by South Gloucestershire Council last year.
A decision has still to be taken on which contractor will carry out the main base build and fit-out.
The new five storey building known as The Approach is presently being marketed to potential tenants as a well connected corporate HQ.
ISG previously occupied the former office buildings on the site for more than 40 years, having originally moved in in 1974.
James Digby, Director at Ashfield Land, said: “Today is about bringing The Approach another step closer and readying the site for redevelopment.
“It’s a major milestone and means we have real momentum as we look to move forward into construction and, ultimately, providing a top quality occupier with a new home here in Bristol.”