Feng Chongyi, a China studies academic at the University of Technology Sydney (UTS), was conducting interviews for a human rights project.
"I'm not scared of them. I did not do anything illegal," he said after he was finally allowed to leave Guangzhou.
Dr Feng is an Australian permanent resident but retains a Chinese passport.
He travelled to China a month ago and was first questioned in Kunming in south-western Yunnan province, before twice being barred from flights leaving Guangzhou.