In a match held over to the venue, the world champion showed all his class as runs of 56, 64 and 102 was too much for the 90th-ranked Liverpool player, whose knock of 51 was merely a consolation against the in-form Welshman.
William will face 1997 world champion Ken Doherty in the last 64.
In the first round of the event, there was a 5-3 win for 2015 world champion Stuart Bingham against the 2002 Crucible winner Peter Ebdon with both men hitting centuries.
China Championship
Selby cleans up to win final frame thriller and punish crucial Higgins error
30/09/2018 AT 16:45
Stephen Maguire lost to fellow Scot Scott Donaldson while Masters champion Mark Allen thumped Matthew Selt 5-1.
China Championship
Huge tension as crucial frame 17 goes down to nailbiting final black
30/09/2018 AT 15:38
China Championship
Higgins holds slender advantage over Selby in China Championship final
30/09/2018 AT 11:45