In the early years of the revolution he became famous for his republican tragedies like Marius (1791) and Lucrèce (1792). The political climate then forced him to leave France but he returned in 1793, risking the guillotine. He took part in Napoleon's campaigns in Italy and Egypt , always displaying a profound admiration for the emperor: this earned him an appointment to the Académie Française (1799), where he was put in charge of public education and served as an adviser on university teaching.

With the collapse of the Napoleonic political regime, Arnault found himself in grave difficulties, losing all the posts he had received and being forced into exile in Belgium . In 1829 he was let back into France and readmitted to the Académie . As well as tragedies, he wrote works of various kinds, such as Vie politique et militaire de Napoléon 1er (1822) and the Nouvelle biographie des contemporains (1822-25).