Yesterday, Khan tweeted a statement that "President Trump got the message" from Londoners who disapprove of his "divisive agenda" after he cancelled a trip to the UK.
During the nonviolent protest, one member announced, "Ladies and gentlemen, we're here today to make a non-violent, peaceful citizen's arrest".
Mr Khan sat down and flicked through a newspaper while police escorted the demonstrators away.
One man shouted "No to the EU" and another displayed a USA flag.Audience members began to heckle and slow-clap, but the protesters resisted attempts to remove them, claiming they would sue anyone who touched them for "common assault".
Trump had claimed he had scrapped the visit because he did not want to open the new United States embassy in the British capital, but Khan on Friday suggested the real reason was because he would not be welcome, CNN reported.
"If you touch us, you'll be done for common assault".
British Foreign Secretary Boris Johnson fired back at Khan on Twitter, saying on Friday that he would "not allow US-UK relations to be endangered" by the London Mayor, whom he referred to as a "pompous puffed up popinjay in City Hall".
"We're not leaving, we've paid for a ticket".
The protesters claimed the Fabian Society was "subverting our English constitution", with one quoting the Magna Carta.
After paying £35 to get in, they said they were "heading to the pub afterwards".
Mr Khan told delegates: "It is a pleasure to be here even though we were distracted by the actions of what some would call very stable geniuses".
They interrupted Khan's speech to the Fabian Society about gender equality.
Mr Trump recently used the words 'stable" and "genius' to describe himself.