Preti was born in Ferrara. He graduated in law in Bologna and lecturer of public law. He died in Bologna in 2009.
Preti was a member of House after fascism, who wrote new Italian republican Constitution. He was Minister of Finance, for International trade, for Budget, for the Reforms of administration and for Transport. He was also president of his party. He retired from politics in 1987 after 40 years in politics.