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Massimo Luongo and Mile Jedinak scored inside the first 12 minutes to have the Socceroos 2-0 at the break before they ran riot in the second half.
It was carnage for the visitors as Mark Milligan scored another penalty early in the second half before Nathan Burns (two) and substitute Tom Rogic scored a brace within five minutes of coming off the bench.
And it could have been an even bigger win for the hosts, who hit the woodwork an astonishing four times in the second half.
Debutant Apostolos Giannou was one of the Socceroos' best, finishing with assists for four of the goals and unlucky not to get one himself with an effort that hit the post in the second half.
Playmaker Aaron Mooy continued his incredible run of form with another brilliant display in the middle of the park while local boy Ryan McGowan and Burns were also strong.
But the green and gold didn’t have a bad player as they rarely got out of first gear, now needing only a point against Jordan on Tuesday to confirm their spot in the next stage of qualifying.
New boy Giannou was handed a debut up front and the 26-year-old made an immediate impact, setting up the opening goal inside two minutes.
Burns played the ball into Giannou at the top of the box, with the striker teeing up Luongo who arrowed a powerful shot into the bottom corner.
Soon after it was 2-0 and Giannou was again involved, racing onto a pinpoint through-ball by Jedinak only to be brought down in the box by keeper Alisher Tuychiev.
An ice-cool Jedinak had no trouble sweeping home from the spot for the skipper’s 12th international goal.
The Socceroos were playing some sublime attacking football. The passing was slick, the touches were assured and the movement off the ball was first-class.
It was the type of play Postecoglou has been craving with his side enjoying the acres of space and time on the ball afforded to them by the out-classed visitors.
Chance after chance went begging and a one-sided first half with Mat Leckie, Burns, Giannou and Jedinak all squandering excellent chances to add to the lead.
Milligan replaced Jedinak at the break and he had his name on the scoresheet within 12 minutes of the resumption.
Giannou was again in the thick of it, hauled down in the box by Ergashev Davronjon for another penalty, which Milligan dispatched with aplomb.
Burns added a fourth 10 minutes later with a simple tap-in but Mooy deserved all the credit.
The exceptional Melbourne City playmaker mesmerised the Tajikistan defence, showing great strength and skill to hold off two defenders before picking out Burns with a delightful cross.
Rogic came off the bench and made an immediate impact, scoring twice in the space of two minutes.
First he was credited with a goal after volleying home Mooy’s free-kick, although replays suggested it might not have crossed the line before Giannou slammed it in.
Before the crowd could catch their breath they were celebrating again as Rogic shimmied past one defender and curled in a classy effort with the outside of his left foot.
Burns then completed the rout three minutes from time with a simple header from McGowan’s cross.
Jordan is now the final hurdle for the Socceroos to overcome to win the group when the two sides meet in Sydney on Tuesday.
Caltex Socceroos 7 (Luongo 2’, Jedinak 12’, Milligan 57’, Burns 67’, 87’, Rogic 70’, 72’)
Tajikistan 0
Crowd: 35,439 @ Adelaide Oval
