Sabalenka looked in great touch against the tricky Czech, who had won their last three meetings and went into the match as one of the few players with a winning record over the world number one.
But Sabalenka showed her class and power as she broke Muchova once in each set to take the semi-final 6-3, 6-4 in 89 minutes.
"I struggled against her a couple of times (in the past)," Sabalenka said.
"I'm happy that today I was focused from the beginning and I was able to show such great tennis and put her under so much pressure and get the win in straight sets."
The 27-year-old Belarusian said she could feel her level getting better with every match in Brisbane, where she is yet to drop a set.
She said that with seven of the world's top 10 having entered, it was ideal preparation for the Australian Open, which begins in Melbourne on January 18th.
Sabalenka is aiming to win a third Australian Open in four years.
"I definitely feel that compared to the first match here, I'm playing better and better," she said.
"That's really important heading to Melbourne, to build that level, and to play some great matches against great opponents."
"So I'm super happy with the performance so far and cannot wait to play my final match here."
Sabalenka, the defending champion, will face the impressive Marta Kostyuk in Sunday's final, after the Ukrainian dismantled Jessica Pegula 6-0, 6-3, meaning she has defeated three top-10 players this week.
Victories over Amanda Anisimova, Mirra Andreeva, and now Pegula will also see her return to the top 20 in the world rankings.
"I think it was one of those days today when everything you touch turns into gold," Kostyuk said.
"Personally, I didn't have many matches like this in my career, especially against top-10 players, so it's a great bonus to have such a match because it's not easy conditions in Brisbane. It's very hot, very humid."
Kostyuk has never beaten Sabalenka in four previous meetings, but said the pressure was all on her opponent.
"The pressure is not on me -- I want to go out there and put on a good show for the crowd," she said.
"I really have nothing to lose."
In the men's draw, top seed Medvedev beat Alex Michelsen of the United States 6-4, 6-2, while Brandon Nakashima defeated another American in Aleksandar Kovacevic, 7-6(4), 6-4.
