The American world number four made a slow start as Muchova broke immediately to take the opening game, but that proved to be the Czech's only moment of clarity. Gauff responded with a break of her own to level and then reeled off the remaining games without dropping a single one, closing out the first set to love in ruthless fashion.
Muchova, 29, had been in fine form coming into the contest, having won the title in Doha earlier this season before defeating Victoria Mboko, in a rematch of that Doha final, in the Miami quarter-finals.
But a flurry of unforced errors undid her in the second set, with Gauff breaking three times to complete a dominant victory while extending her perfect head-to-head record to six wins against the Czech.
Gauff will face either Aryna Sabalenka or Elena Rybakina in Saturday's final, with the two heavyweights scheduled to contest the second semi-final later on Thursday.