The Star Inn, Guildford, was told it must reduce its noise levels after complaints to the council from neighbouring developers.
The pub has been at the heart of the city’s live music scene for decades and was the first gig for punk rock band the Stranglers in the 1970s.
More than 25,000 people signed an online petition calling on the council to rethink the decision.
General manager Georgina Baker said live music was the source of 30% to 40% of its revenue.
She told The Morning Advertiser: “Being served a noise abatement notice puts us at risk of losing nearly half our business, it’s really serious.”
“The venue is such an important part of the fabric of Guildford, it’s where so many of the young bands start out and get their first break and experience of playing on stage.
“To lose that would be devastating for such a huge number of people.
"We're not going down without a fight."
She added: “Small live-music venues are the lifeblood of the music industry as well as an invaluable cultural and social asset, they can’t just be swept aside for luxury apartments.
Shepherd Neame will protest the notice and has received the backing of the city council’s leader Paul Spooner.
A brewery spokesperson said: “Having sought legal opinion from counsel we believe there are sufficient grounds to launch an appeal in the hope of ensuring the restoration of the Back Room at the Star to its full use as a live-music venue.
'Does not mean silence'
A spokesperson for Guildford Borough Council said if a statutory nuisance was found present or likely to recur in an investigation it must issue a notice.
They said: “We have now reached this point in our investigation and served an abatement notice on the regional brewery chain, Shepherd Neame, which owns and manages the Star public house.
“The notice requires the nuisance to stop by reducing noise levels. This does not mean silence and that no noise can be made.
The council has not imposed or specified particular measures to reduce the noise, the spokesperson said.
“It is now up to them to look at the different things that they could do to reduce the current noise levels.
“We are very willing to engage and continue working with both parties, and council officers have offered to meet with the owners to discuss how compliance can best be achieved.”