Liu Xuewu, a teacher at a vocational institute in Guangdong province, spent a large amount of money and two years of his life to get an MBA from a university in Macao six years ago. To his surprise, when he applied to become a professor last year, the evaluation board said his diploma is not acknowledged by China's Ministry of Education

"I never thought it was a diploma mill. I had no choice but to apply for a domestic graduate degree," Liu said.

Since the 2000 crackdown on diploma mills, Sang said he has not heard about any new plans to tackle the problem in Beijing.

He suggested students check the reliability of academic credentials by sending copies to the authentication center of the Ministry of Education, which also has a list of verified universities on its website.

"It doesn't include all the qualified schools but at least it gives people a reliable choice," Sang said.