Adams threw 19.68m to win by 17cm from Michelle Carter of the United States.
Carter opened with a very good 19.51m and it took Adams until round four to edge in front.
Fifty wins in succession is the longest current winning streak in international athletics.
The last time Adams suffered defeat was in August 2010.
She now has a virtually unassailable lead in the Diamond League contest, with 12 points after three rounds. Three other athletes are tied for second on two points.