Influenced by the ideological trend of nationalism, Béla Bartók (1881-1945), an important Hungarian composer in the 20th century, dedicated himself to compositions with native culture. His piano solo work, Improvisations on Hungarian Peasant Songs, Op.20 (1920), is made of traditional Hungarian peasant music. In addition to its melody, mode scale, and the unique rhythm derive from the peasant music, this arrangement is created by using 20th-century compositional technique. Bartók had once claimed that this music piece is the most mature and integrated one among all his transcriptions of folk music. The first chapter of the paper introduces the Béla Bartók¡¦s journey of collecting the folk materials and the musical characteristics of Hungarian folk music, showing its thorough impact on his works. The second chapter discusses the classification of Bartók¡¦s different methods to compose transcriptions of folk music. The third chapter focuses on finding the distinguishing features of Improvisations on Hungarian Peasant Songs, Op.20. The compositional methods about how Bartók made use of the folk music are analyzed from aspects of melodic structure, rhythmic application, and mode scale.