Sylvain holds a degree in law and then worked as a lawyer. In 1934, he was the founder of the anti-communist newspaper " La Croisade " ( The Crusade ). He was also a founder of the " Rassemblement Du Peuple Haitien " ( merger of the people of Haiti ), an underground party. During the reign of Paul Eugène Magloire 1950 to 1956 he was a judge and earned a highly respected reputation after he pronounced a judgment against a close friend of the president in a process.
On 7 February 1957, he was by the Parliament as the successor of Joseph Nemours Pierre -Louis Acting President of Haiti and beat off the wealthy plantation owner Louis DEJOIE as well as those considered to be revolutionary Daniel Fignolé by. However, he had the presidency only 56 days held until he was deposed by General Léon Cantave.
Over his tenure, he wrote memoirs under the title ' " Les Jours 56 De Franck Sylvain "