Elliot Slessor beat Ronnie O'Sullivan for the second time this season - despite a maximum break from the Rocket.
Slessor dominated the opening session to establish a 4-0 lead, but O'Sullivan kept his hopes alive with a fluent 147 which could earn him £42,000 at the end of the week.
However, O'Sullivan will take no further part in the tournament as Slessor won two of the next three frames to reach the second round, in the process securing his second victory in as many matches with the world number one this season.
Slessor had overcome the odds to beat O'Sullivan in Northern Ireland last November, and the world number 73 lived up to his own high expectations to do the business again.
🙌🎱🚀 Ronnie O'Sullivan hit the 14th 147 of his career at the China Open today!
— Sporting Life (@SportingLife) April 3, 2018
But he lost the match 6-2 to Elliot Slessor!pic.twitter.com/pIRAUXayWH
Slessor, 23, told www.worldsnooker.com: "I love playing the top names in front of a crowd, that’s what I practise for. I don’t feel intimidated by them because I know if I play my best, I can compete. I knew Ronnie would come back at me after the interval so I just had to make the most of my chances."
O’Sullivan said: "Elliot played a fantastic match, he kept potting balls and there wasn’t a lot I could do about it. The 147 was nice for me and nice for the fans. Obviously I would have preferred to win the match, but a 147 is a good second prize."
There was also another unexpected result in Beijing, as Chris Wakelin coasted past Shaun Murphy, the world number seven, with a 6-0 victory.
World number one Mark Selby, though, had no such problems as the defending title holder saw off Scott Donaldson 6-4, having cleared 16 reds in the second frame on his way to a break of 141.
In the other evening matches, home favourite Ding Junhui - the world number four - beat Craig Steadman 6-4, with Australian Neil Robertson, Mark King, Xiao Guodong, Kyren Wilson and Welshman Michael White also progressing to round two.
Elsewhere on Tuesday, Scotland's John Higgins, the world number five, saw off Martin O'Donnell 6-2, while Irishman Fergal O'Brien edged out Stephen Maguire 6-5 as Barry Hawkins, Graeme Dott and China's Yan Bingtao also advanced.
The closing matches of the day saw Chinese amateur Luo Honghao pull off an upset when he beat world number 16 Anthony McGill 6-4, while Michael Holt and Tom Ford also safely moved into the second round.
The China Open is the last event ahead of the 2018 World Championship in Sheffield, which begins on April 21.
