The home team never allowed the visitors to get going in their eight-wicket win.
On the back of their eight-wicket victory, they were also able to secure an unassailable 2-0 lead in the three-match series.
The visitors won the toss and opted to bat first, but could manage to reach only 128 all out in 19.2 overs, as Delissa Kimmince (3/21), Georgia Wareham (3/26) and Sophie Molineux (2/17) delivered fantastic spells for the hosts.
Middle-order batters Amy Satterthwaite (30) and Suzie Bates (22) were the only Kiwis to reach double digits on the day. The rest of the batting unit failed miserably against some incisive Aussie bowling.
In the second half, wicketkeeper batter Alyssa Healy (33) and Beth Mooney (24) got their team off to a superb start, putting 51 runs for the first wicket inside 4.3 overs, before Healy, whose innings was glint with five fours and a six, got dismissed off Lea Tahuhu (1/20). Mooney got out soon against Amelia Kerr (1/19).
Skipper Meg Lanning (26*) and Rachael Haynes (40*) then played sensible knocks to see their team through with more than three overs to spare.
The third and final T20I will be played on Wednesday (September 30).
New Zealand women 128/10 in 19.2 overs (Amy Satterthwaite 30, Suzie Bates 22; Delissa Kimmince 3/21, Georgia Wareham 3/26) lost to Australia women 129/2 in 16.4 overs (Rachael Haynes 40*, Alyssa Healy 33; Amelia Kerr 1/19, Lea Tahuhu 1/20) by eight wickets