Sri Lanka Cricket chief Upali Dharmadasa said Ratnayake, who played 23 Tests for Sri Lanka between 1983 and 1992, will take over from Australian Stuart Law -- the assistant coach to Trevor Bayliss who departed after Sri Lanka`s loss in the World Cup final to India.
Law guided the team in the tour of England that concluded this week.
Dharmadasa said Ratnayake`s appointment was only limited to the series against Australia which comprises three Tests, five one-dayers and a Twenty20 international starting next month.
The 47-year-old Ratnayake took 73 Test wickets with his left-arm slinging action.
In the 70 ODIs he played, Ratnayake picked up 76 wickets.
