The partner of a Melbourne woman detained in Beijing for more than two-and-a-half years says Victorian Premier Dan Andrews must raise her plight on an ice-breaking trip to China this week.

Mr Andrews will arrive in Beijing on Tuesday morning for the first visit by an Australian premier to China since 2019.

He gave little advance notice of the four-day visit and is not taking any media with him, but prior to departing said he would not raise concerns about Cheng Lei, a mother of two children who has been jailed since August 2020, because it was "too sensitive".

Her partner Nick Coyle, a businessman previously based in the Chinese capital, rejects that, saying it is important for her 13-year-old daughter and 11-year-old son, both in Melbourne.

"Lei considers Melbourne home, so I think supporting two young Victorian children by making representations to officials in China for regular contact with their mother would be an entirely appropriate thing for a premier to do."

In a media conference on Sunday, Mr Andrews did not name her, but said it was a matter for the federal government, while he instead focuses on economic links, particularly for Victoria's higher education sector.

His office referred a specific question about her from the ABC to his comments on Sunday.

"There are a number of people in custody. I just want to make it very clear, that would not be something that I would raise because they are deeply sensitive matters", he said.

"They're best dealt with by the Australian foreign service.

"Some things are absolutely appropriate to raise. Other things, you need to be very careful when you are the leader of a sub-sovereign state", he said.

Mr Andrews's visit to China will coincide with the one-year anniversary of Cheng Lei's secretive trial in a Beijing court, which took place for only a few hours behind closed doors.

The former anchor and journalist for Chinese government broadcaster CGTN is accused of providing intelligence or state secrets to foreigners or foreign organisations, but Chinese authorities have never publicly disclosed details of her alleged crime.

Australian diplomats were barred from attending her trial because it involved national security allegations, despite a bilateral deal that is supposed to grant them access to cases when Australians are on trial.

The lack of a verdict or sentence in China's government-controlled courts has fuelled speculation that her prolonged incarceration is being used as leverage over Australia by China's government.

Nick Coyle says the situation is "enormously difficult" for both Cheng Lei and her children, and she is not being provided the opportunity to regularly speak to her children.

"Everybody is holding up as well as possible under the circumstances", he said.

"Fortunately, consular visits can now be done face to face rather than video link, which is good, but the ongoing uncertainty is distressing", he told the ABC.

"I think her case really negatively impacts the views of China by many fair-minded Australians," he said.

Another Victorian, actor and father Karm Gillespie, is on death row in a southern Chinese prison after being sentenced to death during the height of diplomatic tensions in 2020.