The 2010 world champion came from 4-8 down to win the final five frames and claim a memorable 9-8 victory.
The Australian claimed his first ranking title since June 2016 despite failing to take the lead until the final frame.
A key moment came in the 16th frame when both players needed to pot the pink and black – but after a shocking miss from Cao, Robertson cleaned up before clinically claiming the 17th.
Cao was participating in his first ever final and Robertson believes that it was his inexperience that ultimately cost him a maiden championship win.
“I have no idea (how I won),” Robertson said.
“I feel terrible. Up until 8-4 he outplayed me.
“He thoroughly deserved to win. Inexperience cost him.
“Cao can’t be disappointed. For a first final it was an incredible effort.”
Meanwhile, runner up Cao said: “It’s not good enough.
“I don’t have a strong heart. Maybe I need more practice.
“From 8-4 Neil played very well. It’s my first final. This time I was very close.
“I can remember today next time.”