Co-organiser Tanesha Bennell said no exemption had been sought for the first rally, which drew about 2000 people.
But the venue for the second event on Saturday has changed to Langley Park to provide people with more space to physically distance.
A WA Police spokesman said the community had a right to voice their concerns through lawful protest activity.
“Police will have a presence at the protests and are urging participants to be mindful of physical distancing to ensure community safety,” he said.
“We will take a measured approach to the circumstances, with the ultimate aim being the safety of the community.”
Rally organisers have urged protesters to bring their own water bottles, face masks and hand sanitiser.
In a social media post, co-organiser Jacinta Taylor-Foster said they were doing everything they could to ensure the safety of everyone participating.
“If you are sick and vulnerable, we urge you to stay home,” she said.
Taylor-Foster said there had been 434 Aboriginal deaths in custody since 1991, and there were also shocking statistics on indigenous education, health and life expectancy.
“Aboriginal people are trying to survive every day of their lives within systems that are not made for us to thrive. This must change now,” she said.
Premier Mark McGowan will not ban the protest but has urged protesters to follow COVID-19 restrictions.
Federal Minister for Indigenous Australians Ken Wyatt said the right to protest was important but community health must not be put at risk.
WA Aboriginal Affairs Minister Ben Wyatt said he was concerned indigenous people, who are more vulnerable to the virus, might travel from the regions for the protest and potentially become exposed.
Taylor-Foster said any politician “feigning concern” should use their position to make beneficial changes.
“Do something about this, so that we don’t have to consistently protest and campaign,” she said.