Australia, who broke Sri Lanka's nine-year record of 260/6 against Kenya in 2007, restricted the hosts to 178 for nine in 20 overs to take the lead in the two-match series.
Maxwell destroyed the Sri Lankan bowling attack with his unbeaten 145 off 65 balls, which was laced with 14 fours and nine sixes, after the visitors were invited to bat first.
Skipper David Warner gave Australia a fiery start with his 28 runs off 12 balls as he put on a 57-run opening partnership with Maxwell to lay a solid foundation.
The opener, who registered his maiden T20 century in his 35th game, found the perfect partner in Usman Khawaja, who scored 36 off 22 balls, as the duo put together 97 runs for the second wicket.
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Maxwell and Head, who scored an 18-ball 45, then put on 109 runs for the third wicket as it was raining boundaries at a packed Pallekele International Stadium.
In reply, Sri Lanka were never in the chase after losing openers Tillakaratne Dilshan and Kusal Perera (4) in the first two overs of the innings.
Pace spearhead Mitchell Starc struck in his very first over to get Dilshan, who is set to retire from international cricket after the second T20, bowled for four.
The pressure of scoring at over 13 runs an over proved just too much for an inexperienced Sri Lankan batting side as the Aussie bowlers kept picking wickets at regular intervals.
Chamara Kapugedara also hit a 25-ball 43, studded with three fours and three sixes, to give some respect to the Sri Lankan total.
Starc and Boland claimed three wickets each as James Faulkner, Moises Henriques and Adam Zampa took one each.
The action now shifts to Colombo for the final T20 on September 9.
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