The 17-year-old Belgian, who became the youngest ever player to qualify for the World Championship this year, trailed the 18-year-old Scot 3-2 before a break of 110.
Donaldson then forged a 5-3 lead but Brecel made a 118 break before following up with a 136 to level the match.
Brecel, who received a two-year Tour wildcard after reaching the Crucible, then won the decider to set up a meeting with Peter Lines.
He must win three more matches to reach the televised last 32 of snooker’s second biggest event.
Qualifying Round One results:
David Grace 4-6 Daniel Wells
Pankaj Advani 6-2 Sam Baird
Chen Zhe 6-1 Sean O'Sullivan
Tian Pengfei 6-4 Joel Walker
Li Yan 4-6 Fraser Patrick
Luca Brecel 6-5 Scott Donaldson
Robbie Williams 2-6 Jamie O'Neill
Michael Wasley w/o Hossein Vafaei Ayouri
Thepchaiya Un-Nooh 6-5 Passakorn Suwannawat
Liam Highfield 6-1 Ben Judge
Ian Burns 6-1 Michael Leslie
Dechawat Poomjaeng 6-3 Simon Bedford
Paul Davison 6-2 Gareth Allen
Zhang Anda w/o Duane Jones
Thanawat Tirapongpaiboon 6-5 Martin O'Donnell
Tony Drago 3-6 Craig Steadman