Honored as "the King of Songs",Franz Schubert is regarded as one of the greatest composers of the 19th century.His piano piece of Impromptu has opened up a new era for romantic piano pieces.Rather than with astonishing enthusiasm,the music conveys emotions with a sincere heart,delicate sentimental moving,extraordinary elegance and elaborate techniques.This paper introduces the background and characteristics of Schubert's Romanticism,and discusses the music style and features of his impromptus,from singing of the song melody,the color of harmony,to the variability of music structure and the diversity of mode or key conversion.