There were also cries of "Behead him!", and "Death to the King" in the protest in Grenoble, in the east of the country.
Those responsible now face up to two years in prison and fines equivalent to £26,000, prosecutors in the Alpine city confirmed on Wednesday.
A mob was videoed in Notre Dame square in Grenoble on Monday, mocking the head of state on the first anniversary of him winning a second term.
"They created an image of the president, and then defiled it, including setting it on fire," said an investigating source.
"The protest – which involved up to 300 people – was part of the social movement against the President’s pension reforms," the source added.
Thousands have taken to the streets of France and gone on strike, in recent weeks against Mr Macron raising the retirement age from 62 to 64, without a parliamentary vote.
Eric Vaillant, the public prosecutor of Grenoble, confirmed that all those responsible for burning the Macron effigy faced a charge of "insulting a person in a public office."
If committed by multiple defendants, this crime is punishable by two years in prison and a fine of €30,000 (£26,000)
The prosecutor confirmed that video evidence was being studied, including chants referring to Mr Macron and Louis XVI, France’s last proper king, who was guillotined in 1793.
After the attack on the Macron image, there were clashes between demonstrators and the police, leading to the "degradation of private property," said Mr Vaillant.
Police are actively searching for those involved in the demonstration, and evidence is being studied to try and identify them, Mr Vaillant added.
Three people were arrested in the Alsace region at the weekend and face trial in September for making obscene gestures in front of Mr Macron.
He is now largely steering clear from close contact with the public during trips to provincial France aimed at "explaining" his hugely unpopular pension reform.
Hundreds of people regularly turn up to greet him banging saucepans - a traditional symbol of political protest in France – and many are being confiscated by police.
With his popularity plunging, Macron has set a 100-day target to relaunch his policy schedule, with Prime Minister Elisabeth Borne due to announce plans on Wednesday.
Mr Macron admitted over the weekend that he may not have been active enough in talking to ordinary people when he pushed the rise in the retirement age through via presidential decree.
Mass protests are expected to bring France to a halt, and cause a widespread threat to public order, on May Day, May 1, on Monday.