The three-time Olympic medallist flexed her muscles at Livigno Snow Park in Northern Italy, unleashing a score of 90.0 in a superbly-executed switchback 1260, which included three-and-a-half rotations.
Wānaka's Sadowski-Synnott appeared relaxed and happy as all six judges scored the run 90.0, leaving the Kiwi well clear of the 29-woman field early on.
The second-best opening score went to Japan's Murase Kokomo on 86.25, with Australia's Ally Hickman third (85.25).
New Zealand's Lucia Georgalli was 11th after scoring 78.25 in her opening run.
The top 12 qualifiers will contest the final on Tuesday morning, based on their combined score - from the best two out of three qualifying runs.
Sadowski-Synnott is competing in her third Olympics and is chasing her first Big Air gold.
A year later, she competed at the Pyeongchang Olympics, claiming a bronze medal in the Big Air.
In Beijing 2022, she made history as the first Kiwi to ever win a Winter Olympic gold medal when she won the snowboard slopestyle title. She followed that up just days later with a silver medal in the Big Air.
On Saturday, Sadowski-Synnott and freeski athlete Ben Barclay were the New Zealand flagbearers at the opening ceremony.
The pair were formally announced as Ngā Pou Hāpai Tāne and Wahine (male and female flagbearers) during a special team gathering at New Zealand Lodge in the Italian town of Livigno.
Sadowski-Synnott said she felt "very honoured" to be selected.
"To share this with Beano (Ben) who I've spent a lot of my career with, not only on my snowboard but off it too, is special. He's just an all-round great human being and I'm proud to be sharing this moment with him," she said.
"I just hope to lead the NZ Team in a way that can make everyone proud, it means a lot to me," she said.
