The first punch was thrown when the protest organiser approached two students after one of them stole his megaphone and threw it.
"I was just shocked and amazed at the rage that a group of people had dared to question the Chinese government and the switch got flicked so quickly.
"It's crazy that something like this is happening at a Queensland university."
Police were called about 1pm and left the scene about 4.30pm but no charges were laid.
A UQ spokeswoman said students and staff could express their views in a lawful and respectful manner on campus.
"One of the roles of universities is to enable open,respectful and lawful free speech,including debate about ideas we may not all support or agree with,"she said.
"Earlier today,in response to safety concerns resulting from a student-initiated protest on campus,the University requested police support.