The Bavarian corridor is 500 to 1000 metres wide and starts at Hof, then runs east of Marktredwitz and Weiden, before concluding at Schwandorf.
BNetzA said the section will be 137km long and will comprise DC cable buried underground.
The agency said it had largely followed a proposal by TenneT, the transmission system operator responsible for this section.
It said the only change is a different route at Marktredwitz, because the course proposed by TenneT cannot be approved under water law.
A 10km section will be bundled with the A93 autobahn route, BNetzA said.
BNetzA president Jochen Homann said: “Determining the corridor for the SuedOstLink is an important step on the way to realising the project.
“We are well on schedule with the approval procedures for the large power lines.”
The next steps will be the federal planning process, after which the exact route of the link within the corridor will be determined, BNetzA said.
SuedOstLink will consists of a total of four sections.
BNetzA said the route corridor for the Eisenberg to Hof section was already defined in October, with the remaining sections to be approved in the first quarter of 2020.
Commissioning of the SuedOstLinks is planned for 2025.