Celebrities, racing personalities and a giant rocking horse have ushered in this year's Sydney autumn thoroughbred carnival at a colourful launch on Wednesday.

New mum and carnival ambassador Rachael Finch was on hand in Sydney's Martin Place for the formalities, looking elegant in a regal gold and cream ensemble, while weatherman James Tobin was dapper in a blue suit.

Proving a fashion forward alternative to the more classic looks, style guru Margaret Zhang opted for a painterly monochrome frock and strappy black heels.

Milliner Nerida Winter, TV personality Sally Obermeder and track fixture Bobby the Bugler rounded out the launch party.

They were joined by The Diva - a giant black rocking horse.

"My advice to all lovers of horse racing is to get in early, whether you are a horse racing afficionado or enjoy the social scene trackside," the Australian Turf Club's Tony Partridge said.

Mr Partridge said the $3.5 million Golden Slipper at Rosehill Gardens - the richest race in the world for two-year-old racehorses - should be a highlight.

The Sydney Carnival runs from March 22 until April 26, with more than $30 million in prize money up for grabs.