Perth Glory's Jamie Maclaren bagged a hat-trick and Melbourne Victory's Connor Pain a double as Aurelio Vidmar's men ran riot.
They took a quick stranglehold on the game in Kaohsiung with Borussia Dortmund midfielder Mustafa Amini firing them into a 13th minute lead with a cracking volley from outside the box.
And it got even better seven minutes later when Victory winger Pain added a second after finishing off a solo run in style.
Starved of possession, Hong Kong struggled to make any impact on the match and it took a fine save to keep midfielder Jackson Irvine off the scoresheet as the Olyroos dominated.
The Olyroos stepped it up after the break and Maclaren made it 3-0 in the 77th minute with Pain netting his second of the night 90 seconds later as Hong Kong's defensive fargility was ruthlessly exposed.
Maclaren truck twice more in the dying minutes to complete his treble.
The Olyroos now face Chinese Taipei on Sunday before meeting Myanmar two days later.
Top spot in Group F would ensure Australia automatic qualification for the final stages of qualifing in Qatar in January next year where a top-three finish would seal its passage to Brazil.