LeBron James – who went into the night with a personal record of 1-8 in opening matches of Finals series – finished one assist short of a triple-double as the Lakers humbled the Heat in the NBA bubble in Florida.
James – who is targeting his fourth NBA Championship up against the franchise with which he won his first two – had 25 points, 13 rebounds and nine assists, while All-Star team-mate Anthony Davis had 34 points and nine rebounds.
Kentavious Caldwell-Pope scored 13 points, with Danny Green contributing 11 for the Lakers, while Jimmy Butler led the way for Miami with 23 points, Kendrick Nunn had 18 and Tyler Herro 14.
The Heat – surprise winners in the Eastern Conference after beginning the play-offs as the fifth seed
– made a blistering start to lead 23-10 but the Lakers soon took charge and had a three-point advantage at the end of the first quarter.
Lakers – who finished the regular season top of the Western Conference as they target a 17th NBA title and first since 2010 – blasted away from Miami with a 34-20 second quarter to lead 65-48 at half-time.
Another strong period, won 28-19, built a 26-point lead heading into the last, when the Lakers eased up and were outscored 31-23.
James made it clear his team could not afford to be so sloppy in the fourth quarter in future games.
In a video posted on the Lakers Twitter account, James said: "We ain't satisfied. I don't like the way we played.
"I liked the way we played in the second quarter (and) third quarter. But the way we ended, that's unacceptable."
In his post-match press conference on nba.com, James added: "We've got so much more work to do. The job is not done, we're not satisfied with winning one game. It's that simple."
Game two of the seven-match series will be held on Friday night.