Giulio Caccini (1551-1618), a remarkable composer in the early Baroque period, is known in western music history for his Le Nuove Musiche as well as its preface, in which Caccini left his famous theory of voice and composition, and his “Amarilli, mia bella” from Le Nuove Musiche is also popular between singers for hundreds of years. Five pieces from Le Nuove Musiche are inquired: “Amarilli, mia bella,” “Fortunato Augellino,” “Udite, udite, amanti”, “Odi, Euterpe,” and “Belle rose porporine.” There are six chapters in this thesis. First, the background of the composer is introduced; furthermore, the theory of voice in the preface to Le Nuove Musiche is discussed and Caccini’s viewpoints on vocal techniques and vocal ornamentation are described. In addition, the background of the poets of the lyrics in Le Nuove Musiche as well as the basic metrics of Italian poetry are presented. Finally, the interpretation of the five pieces are proposed.