Ms Fernandez won more than 50% of the vote – which is enough to win outright in the first round presidential election in October.
In the silver medal position was former President Eduardo Duhalde with Radical Party Senator Ricardo Alfonsin taking out the bronze.
Socialist provincial governor Hermes Binner failed to get a podium finish.
After casting her vote in the southern city of Rio Gallegos, President Fernandez hailed the primary as “historic” and a “qualitative leap” for Argentina.
“We are building a political system that is more transparent, more plural, and in which the people can express their opinion”.
Before the vote President Fernandez, 58, was already the clear favourite to win a second term as president in October’s election.
She will need 40% to avoid a second-round run-off, as long as she also has a 10-point lead over her nearest challenger.
Otherwise, 45% is required to win outright.
It had been expected that Ms Fernandez’s husband and predecessor as president, Nestor Kirchner, would bid to succeed her.
But he died of a heart attack last October at the age of 60 which was a major setback for his re-election bid. There are not many who return from the dead – not even politicians.
President Cristina Fernandez has high popularity ratings in Argentina because of strong economic growth and she has made a genuine attempt to combat poverty.
Of course it has nothing to do with the fact that she is one of the hottest 58 year-olds on the planet. Which is not a very insightful political observation, but most likely, rather true.