The title was the Czech's fourth of the season to add to trophies won in Brisbane, Rome and Eastbourne - moving her ahead of Australian world number one Ash Barty and Canadian Bianca Andreescu for most titles won so far this year.
Pliskova won 74% of her first service points, fired seven aces and broke the Croatian four times in a rain-interrupted match that was initially delayed by more than five hours due to heavy rain.
Martic, who held a superior 4-1 head-to-head record against Pliskova and also beat her at Roland Garros earlier this year, took a 2-0 lead in the first set when she broke the top seed in the opening game.
However, that was the only time Pliskova conceded a break of serve and she soon took control with powerful groundstrokes, using the full width of the court to smash winners and passing shots with precision.
Martic's service game suffered. She won only 53% of her first service points and Pliskova duly took advantage to punish the seventh seed and win five games in a row.
Pliskova's consistency in the baseline rallies was a force to reckon with and Martic had no answer to her superior court coverage, eventually conceding the 96-minute match after saving one championship point.