SA Health Minister Jack Snelling has quit Cabinet less than two weeks after the opening of the new Royal Adelaide Hospital (nRAH) and will resign as a MP at the March election.

Mr Snelling held a press conference to explain that after 20 years in Parliament, it was time to retire and be "emotionally more available to his children".

"I've always done my best to make sure that I provide the time with them, but in a portfolio like health, you can't help but be distracted and sometimes, dare I say it, a little grumpy with the family in a way they don't deserve," he said.

"From now on I won't have those other issues and distractions and now I'll be available to them."

Mr Snelling was first appointed to the Labor Ministry in March 2010 and served as Treasurer between 2011-2013 before becoming the Health Minister in 2013.

He was elected to State Parliament in 1997 as the Member for Playford, which covers suburbs in Adelaide's north.

Mr Snelling has overseen the Government's controversial Transforming Health reform of the city's medical services and facilities.

It included the building of the $2.3 billion new Royal Adelaide Hospital, which is the most expensive building in Australia.

The emergency department officially opened on September 5.

"Given the hospital is now open, it does provide me with an appropriate moment to step away from politics," Mr Snelling said.

Mr Snelling is also the Minister for Health Industries and Minister for the Arts.

The Government will hold a Cabinet meeting and reshuffle on Monday.

Jack Snelling delivers one of his last press conferences as a MP to announce his March resignation. ( ABC News: Simon Christie )

March election a catalyst for decision

He had been preselected to compete against popular local and former Labor MP Frances Bedford in the seat of Florey at next year's election after an extensive redistribution.

"When Frances Bedford, contrary to what she previously indicated, announced she was not going to retire, that did give me pause to rethink, as I went out and doorknocked in the electorate, what I wanted to do with the next four years," Mr Snelling said.

"I'm in my mid-40s ... people aren't Members of Parliament forever."

He said he was "absolutely convinced" he would have won the seat of Florey if he contested the March election.

"I've no doubt about that at all," he said.

"But now is the time for a fresh set of eyes to have a look at the [health] portfolio, and a fresh set of hands to deal with the challenges that a health system is always going to face.

"We have an enormous depth of talent in the parliamentary Labor Party and I'm in no doubt there are people there ready to step into the shows of Health Minister and other ministerial vacancies."

Transforming Health a 'proud' moment

He cited the nRAH, compulsory third-party insurance changes and Transforming Health as his most proud moments serving in Parliament and acknowledged it had been a difficult ride.

"Everything that's worthwhile in political life is difficult," he said.

"But because of the changes with Transforming Health, people who would otherwise have died, will live, people who would have come out of hospital in a wheelchair, will come out walking.

"I know there will be huge benefit to thousands of individual patients with the changes made."

But he rejected the idea that he was walking away just as the role was about to get harder.

"The job will never be done in health. There will always be need for continued reform and change," he said.

Premier Jay Weatherill praised Mr Snelling for his "courageous" work to modernise the healthcare system.

He said future generations would thank him for the changes.

Mr Weatherill called it a "stellar career" and said his "enormous source of wisdom and high-quality judgement had been central to the success of the Government" during his time.