The duo finished with a world record total score of 239.88 -- 84.41 for short program and 155.47 for free skating -- to capture their first-ever Olympic gold.
The pair skated to the song "Bridge Over Troubled Water," a song written by US duo Simon & Garfunkel -- seemingly a nod to their friendship, which has endured an ankle injury suffered by Sui.
Sui and Han, who are the first Chinese figure skaters to win gold in the pairs event since the 2010 Vancouver Games, won silver in this event at the 2018 PyeongChang Games.
"We went through a lot, from being not expected at the very beginning. People said we were a pair of underdogs, because our builds were not meant for figure skating," Sui said following the win.
"Traditionally, men were expected to be tall and women petite," she explained.
"If there is no way in front of us, we will pave our own way, leaving it to others, and that's how we create a legend," she added.
They become the third pair skating team to win Olympic Games gold on home ice following Tatiana Volosozhar and Maxim Trankov of Russia at Sochi 2014 as well as Maxi Herber and Ernst Baier of Germany at Garmisch-Partenkirchen in 1936.
Since the beginning of the 2015-16 season, Sui and Han have finished on the podium at every international competition they have competed in.
This is China's ninth gold medal and 15th overall at the Games, a significant improvement on the one gold secured at PyeongChang four years ago.
China's 15 medals surpass the country's previous high of 11 in Vancouver 2010 and Torino 2006.
The silver medal went to Russian Olympic Committee's (ROC) Evgenia Tarasova and Vladimir Morozov who finished with a total score of 239.25.
Anastasia Mishina and Aleksandr Galliamov of the ROC picked up the bronze after finishing with a 237.71 total score.