The ring was run by Iraqi Kurdish migrants and had a logistics hub in Lille, a northern French city about 100 kilmetres (60 miles) from the northern Channel beaches around Calais that are used for crossings.
Three Iraqi men have been charged, along with three French suspects after their arrest on Monday.
Police discovered “a real factory supplying nautical equipment” in Lille, the head of French anti-migration agency Ocriest, Xavier Delrieu, told AFP.
In what was their biggest ever seizure of equipment, they found 13 inflatable boats, 14 outboard engines, 700 life jackets, 100 pumps and 700 litres of fuel, Delrieu said.
The group is suspected of having organised 80 Channel crossings over the summer, of which 50 succeeded, with the smugglers netting around €80,000 for each one.
The arrests came due to intelligence-sharing between authorities in Belgium, Britain, Germany and the Netherlands, who are all trying to crack down on migrants crossing the Channel by boat.
The original tip-off came after a border guard control discovered a group of French youths carrying inflatables from Germany into the Netherlands.
More migrants have crossed the Channel to the UK from northern France so far this year than in the whole of 2021.
So far this year, more than 30,000 people have been detected crossing the Channel to the UK, fresh government figures showed Thursday. On Wednesday alone, the authorities detected another 667 people.
Britain’s new prime minister, Liz Truss, has faced some criticism from other Conservatives and in right-wing media outlets for not pressing for more French action against the crossings when she met President Emmanuel Macron in New York on Tuesday.
Downing Street said the issue did not come up at their talks on the margins of the UN General Assembly, which instead focused on common ground including Ukraine and energy security.
The crossings are among a host of issues that have badly strained Franco-British relations in recent years.