Turnbull said it was the "largest ever single investment - to protect the reef, secure its viability and the 64,000 jobs that rely on the reef".
The world's largest coral reef system has lost 30 percent of its coral due to bleaching, which is blamed on climate change and pollution.
The half-a-billion dollar investment will go towards changing farming practices in order to improve water quality, and reef restoration research.
Environment Minister Josh Frydenberg, Foreign Affairs Minister Julie Bishop and Assistant Environment Minister Melissa Price will make the announcement in Cairns today.
"Not only does this funding continue to focus on peripheral issues without tackling the real problem, it also ignores the fact that if we continue to roll out the red carpet to projects like the Adani Carmichael mega-mine, it won't matter how much money the government sets aside - the waters will continue to warm".
Environmental groups say the spend on the Greta Barrier Reef is not enough going forward.
$500 million in funding for the Great Barrier Reef announced today is a "game changer" in managing this great natural icon, according to the Great Barrier Reef Marine Park Authority.More news: Why Exxon Mobil Earnings Failed to Meet Expectations
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"It will ensure that we tackle the crown-of-thorns... and use the best available science to ensure our coral is resilient to heat and light stress".
"The funding provides us with a long-term guarantee of a strong on-water presence to manage the Great Barrier Reef World Heritage Area through the on-ground work by our field officers".
"Our elected representatives can't have it both ways", she said.
But it's not just local efforts that are needed, Schubert stressed.
"You can not protect the reef from puddles of warm water sitting over the entire northern GBR, together with all of the cyclones that came at the same time which were also climate-related".
President Donald Trump in 2017 announced that the US would be withdrawing from the historic agreement.
The government will partner with the Great Barrier Reef Foundation in an agreement worth $444 million to mitigate the effects of climate change, reduce pollution, and deal with crown-of-thorns starfish, the coral-eating starfish that can munch their way through corals when they explode in numbers. "If the Turnbull government was serious about saving the reef, they would be willing to take on the industry responsible for the damage".