O'Sullivan took the opening frame but Stevens immediately pegged him back to make it 1-1, suggesting that 'The Rocket' would not have it all his own way.
However O'Sullivan quickly moved through the gears and won the next four frames to put himself in control.
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The seventh frame saw Stevens rack up 37 and, although he lost the table to O'Sullivan, he came back to clean up and force an eighth frame.
However, O'Sullivan took that frame - before attacking the tournament format in his post-match remarks.
"China is where it is at. The money is there, they are ready to pump it in to snooker, they just don't want 128 players," O'Sullivan told the BBC.
"It is anarchy when you go over there (to compete in a 128-player tournament), you watch it and it is just too many players, too many people. They want the cream of the cream - and that is the top 32."
He will now face the winner of the clash between Liam Highfield and Mark Williams.
In the other early game Shaun Murphy, who criticised O'Sullivan for his recent comments on snooker, defeated Zhou Yuelong 6-2.
He will face the winner of Luca Brecel's match against Stephen Maguire.
In the two late games Oliver Lines followed up his 6-0 victory over Jimmy Robertson with a heavy 6-0 reverse against Marco Fu as his run in the tournament came to an end.
Fu will now face the winner of Jamie Jones and David Gilbert.
World number one Mark Selby is also through as he defeated Zhang Anda 6-1 to set up a quarter-final game against either John Higgins or Mark Allen.
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