A further five participants in the race, which took place in Gansu Province, have been reported missing.
It was held on Saturday morning in the Yellow River Stone Forest tourist site in Jingtai County, Baiyin City.
At 3am on Sunday (8pm GMT), the deceased were found and rescue mission to located the missing group began.
The race has been stopped.
Hail, freezing rain and gales affected the race at a high-altitude stage, between 20 to 31 kilometres.