O'Sullivan, who won the Hong Kong Masters seven days ago, put together breaks of 66, 71 and 52 at Belfast's Waterfront Hall to book a showdown with fellow Englishman David Grace.
Defending champion and home favourite Mark Allen also made it safely through, the Northern Irishman beating Chang Bingyu 4-1.
Allen lost a scrappy opening frame but then made breaks of 123, 56, 70 and 108 as he restricted Chang to just one point in the last four frames.
Three-time winner Judd Trump also eased his way into the second round courtesy of a 4-1 victory over Rod Lawler, while Kyren Wilson beat Ken Doherty 4-0 and former world champion Mark Williams made a break of 128 as he recovered from 2-1 down to beat Peter Lines 4-2.
Neil Robertson and Shaun Murphy enjoyed 4-0 wins over Fraser Patrick and Xu Si respectively, while Mark Selby was made to work far harder before overcoming Reanne Evans 4-2.