Red-faced staff at a Queensland school have been forced to cancel a special ceremony to mark its 25th anniversary.

They were planning to open a time capsule that was buried in the grounds of St Kevin's Catholic Primary School on the Gold Coast in 1979.

Assistant Principal Bernadette Swindley says despite days of digging they have been unable to find the one-metre cylinder.

"We can't do anything about it, it's not there," she said.

"We've searched everywhere, we've turned over 60 cubic metres of soil, we've got huge excavators in, and the poor groundsman is pulling his hair out because the garden's been destroyed."