The world number one struggled in the early stages of his match against Adam Stefanow, going 2-0 down before getting on the board with a break of 61.
World champion Selby (pictured) levelled the contest with a 136 and, although his Polish opponent regained the lead by winning the fifth frame, knocks of 113 and 126 put Selby on the brink of victory and he wrapped up the success with an 87.
Judd Trump had no problems as he started his title defence with a 5-0 whitewashing of Jason Weston.
The world No 2 fired in runs of 102, 83, 122 and 135, taking just 72 minutes to set up a last 64 meeting with Ashley Hugill.
"I feel as if I have improved while a lot of players have stayed still," Trump told worldsnooker.com.
"I still have a lot of room for improvement while other players have hit their peak. I’m going to get better every year as long as I keep working hard. I feel my consistency has reached a certain level and I don’t think it can dip before the World Championship."
Shaun Murphy also made three centuries in a 5-2 win over Allan Taylor, knocking in 89, 101, 101 and 104.
Stuart Bingham and home favourite Ding Junhui were 5-3 victors against Scott Donaldson and Sean O'Sullivan respectively, while Mark Williams brushed aside Zhang Anda 5-1.
It was not totally straightforward for Ding who arrived late for his match due to issues with his waistcoat logos and was forced to concede the first frame as a penalty.
However, Joe Perry was an early casualty, going out 5-2 to Iran's Hossein Vafaei, Robert Milkins lost 5-3 to Noppon Saengkham and Northern Ireland Open champion Mark King exited 5-4 to Leeds potter Sanderson Lam.
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