Felix, who suffered an ankle injury in April, powered to victory in a new world leading 49.68 seconds with Phyllis Francis and Natasha Hastings in second and third respectively.
Felix, who is planning the 200m and 400m double,will rest now for 5 days before lining up in the women's 200m heats on Friday.
LaShawn Merritt won the men's 400m in season's fastest time of 43.97.
.@allysonfelix was LIGHTNING fast racing towards the finish line in the 400m tonight!