The All Blacks extended their record winning streak to 42 games with a fifth win out of five events on the IRB World Sevens Series circuit this season and a seventh straight victory, having won the final two in 2007.
Gordon Tietjens' team appear to be on an unstoppable march to an eighth IRB World Sevens Series title in nine years - a run only broken by Fiji in 2006 - having won 30 points in Hong Kong to go 38 points clear of the Springboks in the standings.
And the series could be sealed in Adelaide, the third from last event, next week.
The All Blacks progressed to the knock-out stages with three wins out of three before a 26-7 quarter-final win over Wales and a 34-0 semi-final defeat of Fiji.
Defending champions Samoa, who ousted England 17-12 in the cup quarter-final, were defeated 12-10 by South Africa in the last four.
Lote Raikabula found a gap to cross under the posts just one minute 15 seconds into the final as the All Blacks demonstrated their intent.
Raikabula again burst through the Springboks' defence and off-loaded to Steven Yates, who crossed for his eighth try of the tournament.
Mzwandile Stick collected a loose ball and raced through to score under the posts as South Africa pulled within seven points but Raikabula barged over from close range on the hooter.
Tomasi Cama, the leading scorer on the circuit this season with 188 points, successfully converted for the third time for a 21-7 interval lead.
Zar Lawrence went over on the left wing less than two minutes into the second half to leave the Springboks facing a 19-point deficit which they could not overcome.
South Africa claimed a consolation when Fabian Juries, the leading try scorer in the series with 30, touched down but New Zealand secured a historic triumph.