About 70 cross-country and 90 downhill riders will race the 4km-long course which has an elevation of 226m per lap.
The championships, which are being run by Bike Wanaka Mountain Bike Club, will include UCI and non UCI men's and women's downhill and cross-country races, under-17 boys and girls downhill and cross-country races and masters men's and women's races.
The competition is a selection event towards the Rio Olympics in August.
World under-23 champion and national elite men's titleholder Anton Cooper, of North Canterbury, will be racing against 2014 champion Sam Gaze, of Cambridge, for the only men's qualifying spot on the team.
Gaze said he was in the best shape of his career following a five-week training camp in South Africa under the guidance of coach Christoph Sauser.
"It's the hardest I have ever trained.
"We focused on training my weaknesses which is my climbing ability and my power to weight.''
Queenstown's Kate Fluker is the favourite in the women's cross-country category following wins in last year's national championships in Rotorua, cup series wins in Taupo and Cardrona and her most recent win in the 2016 Motatapu race on March 5.
Former under-23 World Cup winner Samara Sheppard, of Wellington, will return to top-level mountain bike competition today in the lead-up to the Oceania Mountain Bike Championships in Queenstown next weekend.
Cooper said he felt "added pressure'' going into today's race.
"There is definitely added pressure because the Olympics are so close but whatever happens on the day happens.''
He said he had spent an average of 15 hours a week on his bike since November.
"Training-wise, things have gone well.
"I have done all the hard work so whatever the result, hopefully it is clear and the best rider wins and that will simplify things.''
Bike Wanaka president Jamie Greenway, of Wanaka, said he was looking forward to watching competitors on a new track at the park.
The track, which was mapped out "just before Christmas'', was opened to riders just a few weeks ago, he said.
"That was a little nerve-racking doing it that close to such a big event.
"There has been good feedback from everyone that has ridden it, though.
"People are saying it is steep, rocky and technical which are all good things.''
The competition had attracted entrants from as far afield as British Columbia.
However, overall entries in the women's events had been "disappointing''.
"Entries for the downhill women are particularly disappointing this year. There are only four, which is really terrible because we know there are a lot more of them out there.''
Greenway said he believed some women may have been intimidated by the calibre of competition and the technicality of tracks at this level.
This weekend's competition follows on from round one of the New Zealand Mountain Bike Cup Series race which was held at the bike park last January.
