The Olympic bronze medallist clocked a season best of 1:56.56 to outpace Great Britain's Georgia Bell.
Wanyonyi clocked a world leading time of 1:41.11 in Lausanne.
Kenyans have dominated the race through the likes of Wilfred Bungei (Beijing 2008) and world record holder David Rudisha (London 2012 and Rio 2016).
The 100m semifinals will be on Sunday.
Moraa clocked 1:57.91 to win.
World 100m silver medalist Letsile Tebogo and American Courtney Lindsey tied in 200m.
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