The show, Eurovision: You Decide, will be held in Brighton on February 7, during which six acts will perform live before a winning entry is selected based on the views of a panel of music experts and a live public vote.
The Swedish star will co-host the event with presenter and actress Mel Giedroyc.
"I’m really, really looking forward to hosting Eurovision: You Decide together with Mel this year," Zelmerlöw said in a statement published on the BBC website.
"I’m sure we’ll have a great show and I would love to see the UK achieve a great result in Eurovision 2018," he added.
The venue for the show is the Brighton Dome, where Swedish group ABBA won Eurovision in 1974 with "Waterloo".
Zelmerlöw won Eurovision for Sweden in 2015 with the song "Heroes", and co-hosted the event with Petra Mede in Stockholm the following year.
The finals of next year's competition will be held in the Portuguese capital Lisbon on May 8, 10 and 12.