Anti-terror police have launched the crackdown as part of Operation Sentinel, with armed officers patrolling holiday airports.
Bars and restaurants in popular resorts have also beefed up security.
Experts say an attack on French pistes is particularly worrying as a gunshot could trigger avalanches.
Last year, more than a million Brits headed abroad to ski, with February marking peak season.
France is already under a state of emergency following the deadly terror attacks in Paris and Nice.
Security expert Will Geddes, who runs the International Corporate Protection agency, said: “The military and police presence has been flooded right across France.
“They are particularly concerned about any location where there’s going to be a congregation of international visitors.
“It could be a tourist area or one seen as a soft target.
Officers with machine guns have been seen patrolling Chambery Airport, one of the small international hubs that service major Alpine resorts.
At one bar in Val Thorens called 360, staff channelled skiers through wire mesh entrance tunnels and searched backpacks for weapons or devices.
Security experts warned that a lone-wolf attack in the mountains could take many lives.
Mr Geddes added: “There is a real risk of a terror attack being a double threat with avalanches.
“If there was a situation where the military had gone into some sort of gun battle, they would have to be very cautious about where they could safely deploy without the sound repercussion causing an avalanche.
“And if there was to be a major bomb detonation, that would be a huge concern.
It is a very complicated situation.”
