The serve was uneven. She produced seven double faults to four aces, but landed 59% of her first serves and won 33 of 44 points behind that delivery.
The win followed a thin run. After taking just one of her three matches on the Asian swing, Sabalenka took a break before the finals.
Muchova, the Czech, claimed the first break of the opening set. Sabalenka broke straight back, a pattern that repeated through the match.
Sabalenka is bidding to win the season-ending title for the first time, in her sixth appearance at the event.
The second set was topsy-turvy, with five breaks of serve. Sabalenka served the match out on her second attempt.
The Russian reeled off seven games in a row against a wayward Svitolina, backed by her backhand.
By her high standards, the season has been a strange one.
Muchova later served for the first set, but a string of errors forced a tie-break. Further mistakes handed Sabalenka the opener, 7-2.
She said she sometimes had to adjust her toss and sometimes had to serve blind."It's all part of the game,"she said.
Conditions did not help."It was a bit tricky with the sun with the shade,"Sabalenka told Sky Sports.