Australia's Socceroos posted their biggest win under manager Ange Postecoglou with a thumping 7-0 win over Tajikistan to hold their lead in their 2018 World Cup qualifying group in Adelaide on Thursday.

FC Tokyo's Nathan Burns and Glasgow Celtic's Tommy Rogic scored doubles as the Socceroos coasted to within one point of finishing on top of Group B ahead of summit match with Harry Redknapp's Jordan in Sydney on Tuesday.

Australians ran to a 2-0 lead after 12 minutes with goals from Queens Park Rangers midfielder Massimo Luongo and a penalty from Crystal Palace's national team skipper Mile Jedinak.

But the Socceroos were guilty of sloppy finishing and went to halftime still leading by two goals and should have been further in front.

The Asian Cup champions again dominated the second half with new boy Apostolos Giannou earning his second penalty of the game and converted by substitute Mark Milligan in the 57th minute.

The Socceroos were in full cry after that with Burns getting his first off a Aaron Mooy cross and Rogic scoring two quickfire goals in as many minutes just minutes after coming on for Luongo.

Burns rounded off the scoring with a header off a cross from Henan Jianye right-back Ryan McGowan with three minutes of regulation time left.

Australia's win guarantees them to finish in the top two of Group B.

"These games can become difficult, we knew they would sit off (in defence) but having such a quick start and scoring the goal it was just a matter of time before they capitulated," Postecoglou said.

"We missed a fair few opportunities as well which we spoke at half-time about finishing it off and to their credit the players did."