The use of violence against protesters, including children, during the demonstration last month, was "unjustified", prosecutors said in a statement.
More than 80,000 people, many of them Romanians living abroad, marched in the Romanian capital on August 10, accusing the leftwing government of corruption and calling for its resignation.
Police used water cannon, tear gas, pepper spray and batons to disperse the crowd. More than 450 people, including 30 police, were hurt and around 30 arrested.
The police was widely criticised for the way they handled the situation and nearly 800 criminal complaints were filed in the weeks that followed.
A month later, the riot police itself filed a complaint saying there had been an "attempt to change the constitutional order", echoing accusations of a "failed coup" from within the ruling party.
As well as the head of the riot police, two other senior officials in the force and an interior ministry state secretary have been charged with abuse of office.
In a letter to the EU, Prime Minister Viorica Dancila defended the police, saying that the protests had been "an attempt to overthrow a legitimate government with violence".
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