Local MP Matt Turmaine has visited the site to see progress on the £12m preparation programme.
A huge crane has been brought to the site to remove a suite of temporary buildings.
The works will also include the installation of new oxygen supply systems, the demolition of old buildings and undertaking surveys and physical ground investigations over the next 18 months.
Watford General Hospital is one of nine Wave 2 schemes under the revised New Hospital Programme that was published by the Government in January 2025.
Construction of the hospital is estimated to begin between 2032 and 2034 with the project costing £1.5bn-£2bn.
Mayor of Watford, Peter Taylor, said: ‘Any progress on this project is good news. However, the Government's plan is for the construction of the new hospital to only start in 2032 and for this to be completed in 2038, at the earlies. This isn't good enough.
‘The proposal to move cancer services to the Watford site and combine this project with the rebuilding of Watford General, gives us the opportunity to bring this all forward. We have waited so long for Watford General to be rebuilt, and this must happen as soon as possible.'
