Blake, who shocked Bolt with an emphatic win in the 100m on Friday, followed it up with an even more impressive performance in the 200, catching the triple Olympic gold medalist down the stretch before holding him off in the closing metres.
The winner clocked a time 19.80 seconds to a massive roar from a frenzied crowd at the National Stadium. Bolt secured his Olympic spot by taking second in 19.83, grinning as he hugged his training partner in the finish area.
Warren Weir earned the third spot on the Jamaican team, taking third in 20.03.
Shelly-Ann Fraser-Pryce, winner of Friday's 100m in a Jamaican record time of 10.70, also doubled up by powering her way to a convincing victory in the women's 200m in 22.10, with Sherone Simpson a well-beaten second in 22.37.
Veronica Campbell-Brown, the 200m gold medalist in Beijing and Athens, secured the third Olympic spot with a clocking of 22.42 and heads to London bidding to become the first athlete to claim a 200m hat-trick.