Jeremy Zeid, who was standing in Hendon, said President Obama should be "locked up" by the Israelis for "leaking state secrets".
He was referring to the declassifying of documents on Israel's secret nuclear programme.
UKIP said Mr Zeid resigned last week due to health issues.
It is not clear exactly when he resigned, but he made the posts last Wednesday and Thursday.
Raymond Shamash, a surgeon originally from north-west London, was revealed as Mr Zeid's replacement after news of the Facebook posts emerged.
Mr Zeid also said Israel should "do an Eichmann" on President Obama.
Adolf Eichmann was a Nazi war criminal abducted by Israeli agents in 1960 and later hanged for his role in the murders of millions of Jews in World War Two.
Hendon is one of the most marginal seats in the country with the Conservatives defending a majority of 106.
A UKIP parliamentary candidate who said in a Facebook post that Israel should "kidnap" US President Barack Obama has been replaced by his party.