The Birmingham-born presenter will be succeeded as host of the programme by Bob Harris, the former presenter of BBC 2’s Old Grey Whistle Test, from Nov 3.
Harris, 78, who also presents The Country Show on Radio 2, said: “I am proud and honoured to be taking over a BBC Radio 2 institution from a true broadcasting great.
“Johnnie and I have been friends since my years presenting Old Grey Whistle Test and the original Sounds Of The 70s, and I will do everything I can to maintain his legacy and curate the programme with the very best music from that incredible decade.”
The Rock Show’s new presenter will be Shaun Keaveny, 52, the former breakfast show presenter on BBC Radio 6 Music, who is taking over on Nov 1.
Walker began his radio career in 1966 on Swinging Radio England, an offshore pirate station, before moving to Radio Caroline, becoming a household name by hosting its night-time show.
When the station closed, he joined BBC Radio 1 in 1969, continuing until 1976, when he moved to San Francisco to record a weekly show which was broadcast on Radio Luxembourg.
He returned to the BBC in the early 1980s.