"Facebook will work to re-elect Trump and Trump will protect Facebook," the 89-year-old said during a speech at a dinner hosted by his non-profit Open Society Foundation at Davos on Thursday, reports Politico.
"It makes me very concerned about the outcome of 2020," Soros added.
Reacting to his outburst, a Facebook spokesperson said: "This is just plain wrong".
At the dinner speech, Soros called Trump "the ultimate narcissist", and Xi Jinping a "dictator", while praising Swedish activist Greta Thunberg.
Soros also announced he will launch "the most important project of my life" a $1 billion investment in "critical thinking" via a new network of colleges.
Earlier this month, Facebook Vice President Andrew 'Boz' Bosworth claimed that it was the social networking giant that got Donald Trump elected as the US President in 2016 because "he ran the single best digital ad campaign I've ever seen from any advertiser".
In a memo obtained by The New York Times, the key Facebook executive in the same vein suggested that the platform with over 2.45 billion monthly active users should not use its enormous reach to block Trump''s reelection in 2020.
"He (Trump) didn't get elected because of Russia or misinformation or Cambridge Analytica. He got elected because he ran the single best digital ad campaign I've ever seen from any advertiser. Period", said Bosworth who runs Facebook''s hardware group.
"Trump just did unbelievable work," Bosworth wrote.
"As tempting as it is to use the tools available to us to change the outcome, I am confident we must never do that or we will become that which we fear."
Facebook also announced it will show fewer political ads to people on its platform and Instagram, starting with the US which faces Presidential elections this year, but won't ban or limit those as Twitter has already done and Google to some extent.
( With inputs from IANS )