A screen shot shows German Press Agency's story titled "China's number one ladies' detective".

A 57-year-old Chinese woman who helps wronged wives collect evidence of their errant husbands' affairs has caught the attention of international media.

German Press Agency dpa dubbed Zhang Yufen "China's number one ladies' detective" in a story on Thursday, while the Washington Post has traced her affairs-hunting history.

Both reports cite a case in which Zhang unmasked a railway official who had 17 mistresses in different cities after his wife approached her in 2009.

Such efficiency has earned Zhang the nickname "mistress killer".

The media outlets noted that affairs in China often involve a rich, powerful man and a younger woman. A 2012 study by the People's University in Beijing revealed an estimated 95 per cent of Party members investigated for corruption had at least one mistress.

Zhang, herself a victim of infidelity, turned her own experience into a career she has maintained for more than a decade, according to reports.

The Post said Zhang was granted a divorce and received a payout in 2007 after spending five years following her former husband and his mistress.

She founded the Phoenix detective agency in 2003 only charging basic expenses, but was forced to close due to financial difficulties.

Zhang now runs the Alliance Against Mistresses, an organization offering both advice and detective services for betrayed wives, according to the Post.

Judges have refused to recognize her revelations during divorce cases and on occasion evidence she gathered would mysteriously vanish after being submitted to the court, according to the German news wire.

Private detectives have been banned in China since 1993, but sociologist Lin Yinhe said the business is hard to suppress and will grow in future.