The 23-year-old opened with a throw of 20.56 metres which was never bettered and she had the luxury to decline her final throw.
The reigning world outdoor and indoor champion was consistent with her throwing, putting the shot over 20 metres on five occasions.
Her winning throw was a new Oceania and NZ record.
She beat two Belorussians. Natallia Mikhnevich took silver at 20.28 metres and Nadzeya Ostapchuk got the bronze at 19.86.
John Walker's win in the 1,500 metres at Montreal was New Zealand's last gold in Olympic track and field competition.