The personnel will be deployed to the UK in January to join a British-led operation to train Ukrainian troops.
No Australian defence personnel will enter Ukraine.
Australian troops joining Operation INTERFLEX will help prepare their Ukrainian counterparts to continue the fight.
Defence Minister Richard Marles said training the underskilled Ukrainian troops was a vital thing for the nation to be a part of.
"What we're seeing in Ukraine now is really a reservist force, so that's every day Ukrainians signing up to be servicemen and women in the defence forces," he told Nine.
"It's a UK-led initiative ... they're delighted we will be participating in this and this is going to provide basic infantry training. Our personnel will be on the ground in the UK in January."
He said supporting Ukraine was in Australia's national interest as repercussions would have an effect on the whole world.
"We can't allow a situation where a large country can impose itself on a near neighbour not by reference to the rule of law, but by reference to power and might," he told Nine.
"This is developing into a long-term protracted conflict and so we've been very mindful that we need to have support there for Ukraine over the long term and this next tranche of support reflects that."
Prime Minister Anthony Albanese said Australia would continue to stand up for freedom and democracy.
"This is not just about Ukraine's sovereignty - the brave people of Ukraine are defending international law, rules and norms," he said.
The new measures bring the value of Australia's total support for Ukraine to $655 million, including $475 million in military aid.
Australia has donated 90 armoured vehicles.
The additional costs will come from the defence department after Tuesday's federal budget revealed the government will provide more than $210 million to Ukraine over five years.
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