The 22-year-old, who has not competed in major women's big air competitions since winning gold at the Beijing Olympics, finished with 179.00 points, just 1.75 points behind the winner, Canada's Megan Oldham.
"The expectations, I wouldn't say low, but I'm just trying to take it one step at a time going into my first big air competition in four years, and just go out there, ski, and see what happens," Gu said.
It was her second silver medal of the event after a runner-up finish in slopestyle, adding to China's medal tally on the first day of the Lunar New Year, Beijing Time.
"I'm very happy. Today is the first day of the Lunar New Year, the Year of the Horse, and I hope everyone has a great year and success in everything they do," she said.
Taking place at Livigno Snow Park, the final was delayed for more than an hour due to strong winds and snowfall.
Gu started with a strong run that earned her 90.00 points, though a slight slip on her landing in her second run resulted in only 61.25 points, then she rallied under pressure to post an 89.00 in the final.
With the silver, Gu now has five Winter Olympic medals, the most by any female athlete in freeski history. She will also compete in her signature halfpipe event next.
"I'm very happy to win these medals. But each one feels a lot harder than the last," Gu said.
Oldham, who finished fourth at Beijing 2022, claimed gold with scores of 91.75 and 89.00 in her first two runs. This victory marked her second Olympic medal at Milan-Cortina 2026, following a bronze in slopestyle.
"It feels amazing. This is truly a dream come true. I'm so proud of myself for being able to come out here and nail the tricks I wanted tonight, and show my best skiing and make Canada proud," said the 24-year-old Canadian.
Eighteen-year-old Italian Flora Tabanelli wowed the home crowd with her bronze medal win, earning the highest score of the competition, 94.25, on her final run.
