It comes after New Zealand's national finals so any points earned there go toward next season.
"All of New Zealand's top riders are there, trying to get points for next year," Mrs MacLean said.
Riders start arriving from today, and camp at the showground.
When a bullride was held in Hunterville in January, animal advocacy group SAFE urged people not to attend.
It said such events were stressful for animals, and could injure them. SAFE, with the SPCA and Farmwatch, has started a national petition seeking to ban rodeo.
Mrs MacLean hasn't heard there will be any protesters at Raetihi this weekend.
She said it was their right to protest, but they must not come on to the grounds or disrupt traffic.
And she doesn't think there will be anything they would object to.
Mrs MacLean said the Ministry for Primary Industries screened the Waimarino event last year, and everything was passed.
"We're doing everything by the book. We have to - we're farmers. We can't afford to ill-treat stock - that's our livelihood."