Running in lane five, the 2012 Olympic 100m and 200m silver medallist was quickest off the curve and powered away to a big win over Commonwealth Games champion Rasheed Dwyer.
Warren Weir, the 2013 world silver medallist, was third.
Blake's run was his first sub-20 second time since 2012.
"It feels great to be back in the sub-20 club," Blake told Reuters.
"I'm just enjoying the moment and riding the wave of euphoria, and now will head back to training and continue what I'm doing."
Former world champion Blake recorded a season-best 9.90 to capture the national 100m title on Friday, with Olympic champion Usain Bolt having skipped the meeting in his preparations for his farewell at the London world championships in August.
Newcomer Sashalee Forbes ran a personal best 22.71 secs to win the women's 200 ahead of Simone Facey and Jordan Williams.
Danielle Williams, the reigning world champion, produced a confidence-boosting career best 12.56 to win the 100m hurdles.
"I did expect to run something fast coming in, but wasn't sure what it would be. But I'm satisfied with getting under 12.6, I can't complain about getting a personal best," Williams told Reuters.
Olympic and world championship bronze medallist Shericka Jackson returned a season best 50.05 in a close finish to take the 400m title ahead of NCAA champion Chrisann Gordon and 2007 world bronze medallist Novlene Williams-Mills.
"I'm pretty comfortable ... last year this time I was running like 50.4, so I'm really happy with the time at this point of the season, so I will just work with coach (Stephen Francis) to see how much I can improve my PB (personal best) later this year," Jackson told Reuters.
Rio Olympic mile relay silver medallist Nathon Allen dugdeep to hold off a fast finishing Demish Gaye to win his first national 400m title in 44.58.
Shot put world bronze medallist O'Dayne Richards threw 21.29m to retain his national title.
(Editing by Ian Ransom)
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