Lianne Sanderson hit a hat-trick as the champions thrashed Cardiff at Meadow Park.
Vic Akers' side had the game sewn up inside 20 minutes after four early goals. Sanderson struck twice while fellow England internationals Alex Scott and Katie Chapman were also on target.
Jayne Ludlow and Faye White got in on the act before Sanderson completed her hat-trick five minutes after the break.
Gemma Davison grabbed the eighth goal and White doubled her tally as Arsenal maintained their 100 per cent record in the Premier League this season.