He graduated from the University of Bologna with a B.A. in law. In 1936 he obtained his LL.D. from the University of Ferrara.
Luigi Preti was Under-Secretary of State to Treasury at War Pensions Department in 1954. Next, he became Minister for Finance in 1958-1959, then in 1966-1968 and in 1970-1972. Preti was also Minister of Foreign Trade between 1962 and 1963, for the Budget from 1968 to 1969, of Transport and Civil Aviation in 1973-1974, and of Transport between 1979 and 1980.
Preti also worked as a lawyer and a professor of philosophy and pedagogy.
Preti was minister of Italian Democratic Socialist Party.
He was a member of Constituent Assembly in 1946-1947 and a member of Chamber of Deputies since 1947.
He married Anna Fabbri. The couple has 3 children: Paolo, Maria, and Antonio.