The pair established their lead in the first round and finished with 359.10 points.
North Korea's Jo Jin Mi and Kim Mi Rae took silver with 315.90 and Britain's Andrea Spendolini Sirieix and Lois Toulson captured bronze with 304.38.
Quan and Chen, both second-time Olympians, won the synchronised gold medal for the first time as a pair.
Their victory came as little surprise given Quan and Chen have won nine world titles since teaming up in 2022.
The pair dominated Wednesday’s event from the beginning, taking a lead of nearly 15 points after the first two dives, but neither was satisfied with their performance despite the win.
"I'm not happy about our performance. All the dives were mediocre," Quan told reporters.
"Before the event I felt a bit nervous and some pressure. I didn't manage these emotions well," Chen said.
"My performance was a bit unstable and I didn't handle some of the details in the dives well," she added. "It was the Olympics after all. Who wouldn't feel the pressure?
North Korea's 19-year-old Jo and 23-year-old Kim were little known before this year. The pair, who took second place in the Doha World Championships in February, were also critical of their own performance on Wednesday.
"We are not satisfied with the silver medal. We really wanted to give gold to our country but the performance was not done as we expected, as we tried, so we have some regrets about it. But we are still happy and excited," said Kim.
Canada's Caeli McKay and Kate Miller, who were ranked third before the final round, lost their place on the podium after their last dive went out of sync.
The British duo were delighted when they learned they had won bronze, their first Olympic medal.
"I've never shook more in my life than waiting for that result to come up," said Spendolini Sirieix. "We were so happy. After we finished our competition, we were smiling. We did a small prayer, I just gave it to God because I was just like, whatever happens, I'm content. I'm happy."
Quan became China's overnight sensation at the age of 14 when she won gold in the individual 10-metre platform event three years ago at the Tokyo Games.
Chen, who took the silver behind Quan, won the synchronised event in Tokyo with then partner Zhang Jiaqi.
Quan and Chen walked on to the top of the Paris podium to loud cheers and chanting from Chinese spectators who were waving dozens of the country's flags.
