The Swede was no less than 0,236 seconds faster than Esteban Ocon.
The vice European champion Felix Rosenqvist secured the second position behind Alex Lynn in the race on the 6.12 km long city course.
Team-mate Jordan King also improved on his position from qualifying, working his way up into seventh place.
Marciello on pole, Rosenqvist and Lynn 2nd and 3rd respectively.
Pole winner Felix Rosenqvist aims for his second RTL GP Masters of Formula 3 Zandvoort title in The Netherlands.
Lynne Waite and Stella-Maria Thomas
Lynne Waite and Stella-Maria Thomas, BF3 Correspondents