It will be alleged the man, from Narre Warren South in south east Melbourne, picked up a traffic bollard and threw it at the officers.
The bollard hit a female senior constable who was facing the other direction and unable to protect herself.
The man left the scene and the officer was treated for injuries to her neck and head.
Police say these injuries require ongoing medical treatment.
More than 1,000 people attended the protest in Melbourne last Saturday.
Meanwhile, a mystery Victorian virus case has been linked to a apartment complex outbreak.
The state yesterday recorded three new local cases of COVID-19.
All community sport in Victoria has finally been given the green light to resume today after emerging from the state’s two weeks of lockdown. But spectators will not be permitted.