Mr Rennie will claim the Lib Dems are “on the up” after the party made progress in Scotland at June’s general election.
The election saw the Lib Dems take four seats, an improvement from the near wipe-out they suffered in 2015 when voters punished them for going into government with the Tories.
Ahead of conference, Mr Rennie said: “Scottish Liberal Democrats have seen significant gains over the last few years. We are growing again and we have momentum. We have some fantastic new elected representatives who are going to drive the party forward. We have a new leader in Vince whose experience as an important economic thinker is a real asset.
“The Conservatives are struggling in Westminster, Labour is leaderless in Scotland and the SNP are heading down the polling ladder. Liberal Democrats however can make a real difference to the future of our country. Our message in June was about investing in people in health and education. Going forward we will build a fresh, bright platform for changes with the aspiration of creating an open, liberal, environmentally friendly, economically sustainable and fair society.”