According to the report, Roma and African rough sleepers are more than twice as likely to be moved on as white European homeless people.
"The police's behaviour is surprising, there are a relatively high number of reported cases of racist comments and sometimes excessive use of force," Kristin Høgdahl, from the institute, told Norway's state broadcaster NRK.
Oslo introduced its ban on sleeping outside in 2013, giving police a new tool to wake up homeless people they see sleeping outside.
Many of the respondents also reported that their personal belongings and identity papers were wrongfully confiscated and that the police used excessive force and racist language.
We are constantly asked for identity papers, we are strip searched. They say 'go away Romanians', 'If you don't like it, go back to Romania'," one respondent said according to the report.
The Oslo police say that they have not received any official complaints about their conduct.
"We cannot see that we have received and complaints about derogatory or racist treatment of the homeless, nor have organisations who work with them like the Salvation Army and the Church City Mission complained," Johan Fredriksen of the Oslo Police wrote in an e-mail to NRK.