Seventeen staff members and two former employees of Crown Resorts will face trial in a Shanghai district court today, eight months after being detained for alleged gambling crimes.

Among them are three Australians, including Melbourne-based executive Jason O'Connor, Beijing-based international marketing director Jerry Xuan, and colleague Pan Dan.

Another senior executive, Malaysian national Alfread Gomez, is among the defendants who are expected to be tried as a group for vaguely-defined "gambling crimes".

Lawyers acting on behalf of the some of the clients have declined to detail the allegations, citing instructions from Crown not to speak to the media.

But in a statement, Crown says the group are charged with offences related to the promotion of gambling, which is illegal in mainland China.

Jason O'Connor, pictured here with his family, is currently detained in Shanghai. ( Supplied )

The defendants are facing a maximum sentence of three years in jail.

Some family members and Australian consular officials will attend the trial at the low-level Baoshan District Court, but officials say the courtroom is too small to allow Australian media in.

Today's hearing will not involve a verdict or a sentence, and relatives of the defendants have been told to expect a wait of several weeks.

China's criminal courts have a notoriously high conviction rate of 99 per cent.

Experts say prosecutors routinely drop cases before they get to trial if they are not confident of securing a conviction.

In a similar case two years ago, a group of South Korean casino staff spent between 14 and 16 months behind bars while under investigation for illegally promoting gambling in China.

They were eventually deported with little fanfare.