They will join Ding Junhui in what will be a strong Chinese contingent at the Crucible, with the possibility of Liang Wenbo, Yu Delu and Hong Kong's Marcu Fu joining that trio if they come through their matches tomorrow.
Cao, age 21 from Guangzhou, is playing his debut season on the main tour, having won the Asian under-21 title last year. This is the first time he has qualifed for the final stages of a ranking event - and what a time to do it.
He edged out Tom Ford 10-9 in an exciting match to earn a place in the last 32. With the score at 2-2, Ford was docked a frame for returning late to the table after the interval. Cao led 5-4 after the first session and there was never more than a frame in it until he won three in a row from 7-6 down to lead 9-7.
Leicester's Ford made a 107, his second century of the match, in getting back to 9-9, but Cao dominated the decider with breaks of 39 and 58.
"I'm happy, Tom was unlucky and I played well," said Cao, who is based in Sheffield where he practises with Ding and other Chinese players. "I wasn't nervous in the last frame, I just tried to play the balls."
Liu earned his second visit to the Crucible by beating Jamie Cope 10-7. From 5-4 down, Liu won four frames in a row with top breaks of 71 and 138 to go 8-5 ahead. Cope won the next two with a top run of 107 to draw within a frame, but World No 57 Liu took the 16th with a break of 80 and sealed victory in the next.
Liu, now age 21, first qualified for the Crucible in 2008, becoming only the fourth 17-year-old to compete at the famous venue. He drew his idol Ronnie O'Sullivan in the first round and lost 10-5.
Ball by ball scoring and results from tournaments