The 22-year old U.S skier from Vail, Colorado, finished the two legs in one minute 53.07 seconds, a staggering 1.59 seconds ahead of Swiss runner-up Wendy Holdener, with Sweden's Frida Hansdotter climbing from fifth to third after a fine second run.
Shiffrin, who won her maiden overall World Cup title last season, tops the standings with 1081 points and is also in the driving seat in the slalom on 580 points with the Feb 9-25 Games in South Korea's Pyeongchang beckoning.
She set the pace after starting fourth out of the blocks in the opening leg and carved out an advantage of 1.41 seconds over Holdener and 1.61 ahead of Slovakia's Petra Vlhova.
Heavy snowfall on a soft course in the second leg, when the top 30 skiers start in reverse order, did not deter the American as she produced another flawless run to cross the finish line as the event's emphatic winner.
Shiffrin is widely expected to retain the Olympic slalom title she won at the 2014 Games in Sochi, Russia, as well as to have a shot at gold medals in the giant slalom and Super G.
Earlier on Wednesday, former American great Bode Miller heaped praise on his compatriot in an interview with Reuters.
"I think she's maybe the best ski racer I've ever seen, male or female," said the 40-year-old. "She's so balanced, dynamic, intense and focussed, so for me, I think she's got a chance in any event she skis in."
(Writing by Zoran Milosavljevic; Editing by Ian Chadband)
