AFP is reporting that the man, from the Haute-Savoie region, strongly resembles an identikit image of a motorcyclist seen near the murder scene.
Officers are using metal detectors to search a garden 10km (6 miles) away.
Saad al-Hilli, 50, an Iraqi-born British citizen, was found dead in his BMW car; his wife Iqbal, her mother and a French cyclist were also killed.
AFP is also reporting that sources close to the inquiry say the man arrested, who is in formal custody, is a former police officer.
It reports the man, described as a quiet type who liked guns, was dismissed from the police in June last year.
Meanwhile, a garden in Talloires, a small town on the east shore of Lake Annecy, is being searched by police.