Construction work on the site is expected to start in the Autumn of 2015.
Matthew Kershaw, Chief Executive of the Brighton and Sussex University Hospitals NHS Trust said: “The approval of our Business Case is fantastic news for our patients and staff.
“We have been working on the plans for this redevelopment for six years. We can now move forward with confidence into the next phase which will lead to the final approval of the project and make our plans a reality.
“The redevelopment will also provide employment opportunities during the construction phase which will benefit Brighton & Hove and the wider region.”
Over the coming months temporary buildings will be constructed on the site to house clinical services currently in the redevelopment area.