The principal of prestigious Victorian school Geelong College has resigned after allegedly being caught looking at pornography on a school computer.

The college alleges a student saw Andrew Barr looking at pornography while at the school, and said it became aware of the incident just before Easter.

Mr Barr tendered his resignation and the school is now looking for a new principal.

In a statement, the chairman of Geelong College Council, Dr Hugh Seward, said the alleged incident was a breach of the school's standards.

"The council immediately looked into the matter and when our concerns were confirmed, Andrew Barr tendered his resignation," Dr Seward said.

He said the school community had begun looking for a new principal, ahead of students' return to the school on Tuesday, when school holidays end.

"I would like to emphasise that our college community is hurting and we have concern for the welfare of the young Barr family," he said.

"But we must deal with our difficult situation."

Mr Barr is a former chairman of the Association of Heads of Independent Schools of Australia, and joined Geelong College in 2013 from Scotch Oakburn College in Tasmania.

A boarding school founded by the Presbyterian Church of Victoria in 1861, the college has about 1,300 students aged between three and 18.