Trump made the perfect start with a break of 116 in the opening frame, but struggled in the next four frames, scoring a combined 54 more points as Liang surged to within one frame of victory thanks to breaks of 55, 96 and 118.
A break of 59 helped Trump reduce the deficit and increase the pressure on Liang, who ran out of position when looking set to seal victory in frame seven and then played a loose safety on the last red to let Trump in to clear up.
Trump also took a scrappy eighth frame and made 72 in the decider to seal a hard-fought win and set up a meeting with Liang's compatriot Zhou Yuelong, who also needed a decider to see off Luca Brecel.
Ali Carter produced a superb comeback to beat Matthew Stevens 5-4, the two-time World Championship runner-up recovering from 3-0 and 4-3 down to edge a high-quality contest.
Stevens made breaks of 67, 104 and 68 to seemingly take control of the match, but Carter replied with runs of 74, 78 and 90 to level the scores.
A break of 63 edged Stevens back ahead, only for Carter to respond with contributions of 98 and 60 to advance.
Earlier in the day, former world champion Shaun Murphy beat Jimmy Robertson 5-3, Yan Bingtao edged Elliot Slessor 5-4 and Jak Jones made breaks of 94 and 50 in the last two frames to beat Hossein Vafaei by the same score.
Ding Junhui made breaks of 73, 105 and 100 as he reeled off the last four frames to beat Kyren Wilson 5-3.