The Greens must prepare to become a "party of government" as Australia's two-party political system breaks down, according to Greens leader Richard Di Natale.

"Our vote is already matching it with the Coalition and Labor amongst young voters," he will tell the Greens' national conference in Adelaide on Saturday.

"My goal is for the Greens to be a party of government, and like you I look forward to congratulating the first Greens prime minister."

Senator Di Natale will ask conference delegates to "explore what the Greens' role in a multi-party government looks like ... and how to get there".