A decision by the Constitutional Council is expected on Friday into whether the pensions measure meets constitutional standards.
Marchers in Paris rallied near the Council at the Palais Royal gardens near the Louvre museum and briefly stormed the headquarters of luxury company LVMH.
Fabien Villedieu of the Sud-Rail Union said LVMH “could reduce all the holes” in France's social security system.
“One of the solutions to finance the pension system is a better redistribution of wealth, and the best way to do that is to tax the billionaires,” said Mr Villedieu, referring to Bernard Arnault, head of LVMH and one of the country’s richest people.
Piles of rubbish in the streets also signalled the start of a new strike by refuse collectors, timed to begin with the protest marches.
A previous strike last month left the streets of the French capital filled for days with mounds of reeking refuse.
Thousands also marched in Toulouse, Marseille and elsewhere. Tensions mounted at protests in Brittany, notably in Nantes and Rennes where a car was burnt.
“The mobilisation is far from over,” said CGT union leader Sophie Binet at a rubbish incineration site south of Paris.
“As long as this reform isn’t withdrawn, the mobilisation will continue in one form or another.”
CGT has been a backbone of the protest and strike movement challenging Mr Macron's plan to increase France's retirement age from 62 to 64. Eight unions have organised protests and student unions have joined in.
Mr Macron initially refused a demand to meet unions, but during a state visit on Wednesday to the Netherlands he proposed “an exchange” to discuss the follow-up to the Constitutional Council decision. There was no formal response to his offer.
The nine member constitutional court is made up of former politicians and senior civil servants.
It will rule on the law and an opposition-backed request to put the reform to a referendum.
Opinions polls have consistently shown a majority of French people are opposed to the pension reform.